1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods. 2. Epoxidation of cembrene at the C11–C12 double bonds under the conditions used takes place preferentially as compared with epoxidation at the C7–C8 double bond.