Benzo [c] phenanthrene (1) is a relatively weak carcinogen'widely distributed in the environment. 2 Metabolism of 1 on the benzo ring occurs almost exclusively at the 3, 4- position to give trans-benzo [c] phenanthrene-3, 4-diol3 (2), the precursor to the bay region benzo [c]-phenanthrene-3, 4-diol 1, 2-epoxides (BcPhDE). BcPhDE exists as a pair of diastereoisomers: syn-BcPhDE (3) and