This excerpt taken from the SHOR DEF 14A filed Jan 2, 2009.
Vesting of New Options
Regardless of the extent of the vesting of the existing out-of-the-money options, new options will vest over a new period of four years, with either (i) 25% of the shares subject to the option vesting on the first anniversary of the grant, and the remainder vesting ratably each month over the next three years, or (ii) 50% of the shares subject to the option vesting on the second anniversary of the date of grant, and the remainder vesting ratably on a monthly basis over the next two years. The particular vesting schedule would be determined based on the vesting schedule of the surrendered option and whether its was a new hire grant, which has one year cliff vesting or a
follow-on grant, which has two year cliff vesting. The continued vesting of the new options is subject to continued employment of the recipient with ShoreTel or its subsidiaries.