This excerpt taken from the PDEX DEF 14A filed Oct 26, 2006.
Holders of NQOs do not realize income as a result of a grant of the option, but normally realize compensation income upon exercise of an NQO to the extent that the fair market value of the shares of Common Stock on the date of exercise of the NQO exceeds the exercise price paid. The Company will be required to withhold taxes on ordinary income realized by an optionee upon the exercise of a NQO. In the case of an optionee subject to the "short-swing" profit recapture provisions of Section 16(b) of the Exchange Act, the optionee realizes income only upon the lapse of the six-month period under Section 16(b), unless the optionee elects to recognize income immediately upon exercise of his or her option.
Holders of ISOs will not be considered to have received taxable income upon either the grant or the exercise of the option. Upon the sale or other taxable disposition of the shares, long-term capital gain will normally be recognized on the full amount of the difference between the amount realized and the option exercise price paid if no disposition of the shares has taken place within either two years from the date of grant of the option or one year from the date of exercise. If the shares are sold or otherwise disposed of before the end of the one-year or two-year periods, the holder of the ISO must include the gain realized as ordinary income to the extent of the lesser of the fair market value of the option stock minus the option price, or the amount realized minus the option price. Any gain in excess of these amounts, presumably, will be treated as capital gain. The Company will be entitled to a tax deduction in regard to an ISO only to the extent the optionee has ordinary income upon the sale or other disposition of the option shares.
Upon the exercise of an ISO, the amount by which the fair market value of the purchased shares at the time of exercise exceeds the option price will be an "item of tax preference" for purposes of computing the optionee's alternative minimum tax for the year of exercise. If the shares so acquired are disposed of prior to the expiration of the one-year and two-year periods described above, there should be no "item of tax preference" arising from the option exercise.