Sigma-Aldrich (SIAL)

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities with regard to (1) the integrity of the Company’s financial statements, (2) the Company’s compliance with legal and regulatory requirements, (3) the independent registered public accountant’s qualifications and independence, (4) the performance of the Company’s internal audit function and independent registered public accountant, and (5) the Company’s accounting and financial reporting processes and audits of the Company’s financial statements. Additionally, the Committee has responsibility to prepare the Report of Audit Committee that Securities and Exchange Commission rules require to be included in this annual proxy statement. This report begins on page 42. The Committee is also directly responsible and has sole authority for the appointment, compensation, retention and oversight of the Company’s independent registered public accountant and meets with Company management, the internal auditors and the independent registered public accountant to (1) review the Company’s financial statements contained in the Company’s public earnings reports and the Company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q, (2) review major issues regarding significant financial reporting matters and judgments made in connection with the preparation of the Company’s financial statements, (3) review legal matters that are reasonably likely to have a material effect on the Company’s financial statements, (4) review disclosures made by the Company’s Chief Executive Officer and Chief Financial Officer during their certification process for the Form 10-K or Form 10-Q’s,

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(5) discuss the adequacy and effectiveness of the Company’s internal financial controls and disclosure controls and procedures, (6) approve the annual internal audit plan and (7) receive regular reports of major findings by internal audit and of how management is addressing the conditions reported. The Board of Directors has determined that Committee Members meet the Nasdaq Global Select Market independence requirements and that Mr. W. Lee McCollum is an “audit committee financial expert”, as defined in Item 407(d) of Regulation S-K under the Exchange Act.

In meeting the Company’s Business Ethics Policy, Directors are expected to avoid any situations that may lead to a conflict between their personal interests and the interests of the Company. Should a potential conflict of interest arise, Directors are required to report the potential conflict in writing within 10 days to the Chair of the Audit Committee of the Board. Each situation will be reviewed to determine if the Director’s duties require making decisions that could be influenced by the potential conflict reported. If it is determined that a conflict of interest exists, the Director will be asked to eliminate the situation creating the conflict or to resign from the Board.

The Committee operates pursuant to a written charter, which can be viewed on the Company’s website, www.sigma-aldrich.com. Information on our website does not constitute part of this proxy statement. Any shareholder desiring a copy of the Company’s Audit Committee Charter will be furnished a copy without charge upon written request to the Secretary.

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities with regard to (1) the integrity of the Company’s financial statements, (2) the Company’s compliance with legal and regulatory requirements, (3) the independent registered public accountant’s qualifications and independence, (4) the performance of the Company’s internal audit function and independent registered public accountant, and (5) the Company’s accounting and financial reporting processes and audits of the Company’s financial statements. Additionally, the Committee has responsibility to prepare the Report of Audit Committee that Securities and Exchange Commission rules require to be included in this annual proxy statement. This report begins on page 41. The Committee is also directly responsible and has sole authority for the appointment, compensation, retention and oversight of the Company’s independent registered public accountant and meets with Company management, the internal auditors and the

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independent registered public accountant to (1) review the Company’s financial statements contained in the Company’s public earnings reports and the Company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q, (2) review major issues regarding significant financial reporting matters and judgments made in connection with the preparation of the Company’s financial statements, (3) review legal matters that are reasonably likely to have a material effect on the Company’s financial statements, (4) review disclosures made by the Company’s Chief Executive Officer and Chief Financial Officer during their certification process for the Form 10-K or Form 10-Q’s, (5) discuss the adequacy and effectiveness of the Company’s internal financial controls and disclosure controls and procedures, (6) approve the annual internal audit plan and (7) receive regular reports of major findings by internal audit and of how management is addressing the conditions reported. The Board of Directors has determined that committee members meet the Nasdaq Global Select Market independence requirements and that Mr. W. Lee McCollum is an “audit committee financial expert”, as defined in Item 407(d) of Regulation S-K under the Exchange Act. The Committee operates pursuant to a written charter, which can be viewed on the Company’s website, www.sigmaaldrich.com. Information on our website does not constitute part of this proxy statement. Any shareholder desiring a copy of the Company’s Audit Committee Charter will be furnished a copy without charge upon written request to the Secretary.

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities with regard to (1) the integrity of the Company’s financial statements, (2) the Company’s compliance with legal and regulatory requirements, (3) the independent registered public accountant’s qualifications and independence, (4) the performance of the Company’s internal audit function and independent registered public accountant, and (5) the Company’s accounting and financial reporting processes and audits of the Company’s financial statements. The Committee is directly responsible and has sole authority for the appointment, compensation, retention and oversight of the Company’s independent registered public accountant and meets with Company management, the internal auditors and the independent registered public accountant to (1) review the Company’s financial statements contained in the Company’s public earnings reports and the Company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q, (2) review major issues regarding significant financial reporting matters and judgments made in connection with the preparation of the Company’s financial statements, (3) review legal matters that are reasonably likely to have a material effect on the Company’s financial statements, (4) review disclosures made by the Company’s Chief Executive Officer and Chief Financial Officer during their certification process for the Form 10-K or Form 10-Q’s, (5) discuss the adequacy and effectiveness of the Company’s internal financial controls and disclosure controls and procedures, (6) approve the annual internal audit plan and (7) receive regular reports of major findings by internal audit and of how management is addressing the conditions reported. The Board of Directors has determined that committee members meet the Nasdaq Stock Market independence requirements and that Mr. W. Lee McCollum is an “audit committee financial expert”, as

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defined in Item 401(h) of Regulation S-K under the Exchange Act. The Committee operates pursuant to a written charter, which can be viewed on the Company’s website, www.sigmaaldrich.com. Information on our website does not constitute part of this proxy statement. Any shareholder desiring a copy of the Company’s Audit Committee Charter will be furnished a copy without charge upon written request to the Secretary.

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities with regard to (1) the integrity of the Company’s financial statements, (2) the Company’s compliance with legal and regulatory requirements, (3) the independent registered public accountant’s qualifications and independence, (4) the performance of the Company’s internal audit function and independent registered public accountant, and (5) the Company’s accounting and financial reporting processes and audits of the Company’s financial statements. The Committee is directly responsible and has sole authority for the appointment, compensation, retention and oversight of the Company’s independent registered public accountant and meets with Company management, the internal auditors and the independent registered public accountant to (1) review the Company’s financial statements contained in the Company’s public earnings reports and the Company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q, (2) review major issues regarding significant financial reporting matters and judgments made in connection with the preparation of the Company’s financial statements, (3) review legal matters that are reasonably likely to have a material effect on the Company’s financial statements, (4) review disclosures made by the Company’s Chief Executive

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Officer and Chief Financial Officer during their certification process for the Form 10-K or Form 10-Q’s, (5) discuss the adequacy and effectiveness of the Company’s internal financial controls and disclosure controls and procedures, (6) approve the annual internal audit plan and (7) receive regular reports of major findings by internal audit and of how management is addressing the conditions reported. The Board of Directors has determined that committee members meet the Nasdaq Stock Market independence requirements and that Mr. W. Lee McCollum is an “audit committee financial expert”, as defined in Item 401(h) of Regulation S-K under the Exchange Act. The Committee operates pursuant to a written charter, which was included as Appendix A to the Company’s March 29, 2004 Proxy Statement.

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities with regard to (1) the integrity of the Company’s financial statements, (2) the Company’s compliance with legal and regulatory requirements, (3) the independent registered public accountant’s qualifications and independence, (4) the performance of the Company’s internal audit function and independent registered public accountant, and (5) the Company’s accounting and financial reporting processes and audits of the Company’s financial statements. The Committee is directly responsible and has sole authority for the appointment, compensation, retention and oversight of the Company’s independent registered public accountant and meets with Company management, the internal auditors and the independent registered public accountant to (1) review the Company’s financial statements contained in the Company’s public earnings reports and the Company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q, (2) review major issues regarding significant financial reporting matters and judgments made in connection with the preparation of the Company’s financial statements, (3) review legal matters that are reasonably likely to have a material effect on the Company’s financial statements, (4) review disclosures made by the Company’s Chief Executive Officer and Chief Financial Officer during their certification process for the Form 10-K or Form 10-Q’s, (5) discuss the adequacy and effectiveness of the Company’s internal financial controls and disclosure controls and procedures, (6) approve the annual internal audit plan and (7) receive regular reports of major findings by internal audit and of how management is addressing the conditions reported. The Board of Directors has determined that committee members meet the Nasdaq Stock Market independence requirements and that Mr. W. Lee McCollum is an “audit committee financial expert”, as defined in Item 401(h) of Regulation S-K under the Exchange Act. The Committee operates pursuant to a written charter, which was included as Appendix A to the Company’s March 29, 2004 Proxy Statement.