Three isomeric humulene epoxides (I–III) were oxidized withm-chloroperbenzoic acid to their corresponding diepoxides (A–E) to determine the positions of the epoxide rings of the five known diepoxides. Humulene epoxide I gives three diepoxides designated A, B, and C. Epoxide II gives diepoxides A, B, D, and E. Epoxide III gives C, D, and E. Therefore, diepoxides A and B have epoxide rings in the positions of the monoepoxides I and II, diepoxide C in positions I and III, and diepoxides D and E in positions II and III. X-ray analysis of purified humulene diepoxide A showed it to have the epoxide rings trans, therefore the rings of B must be cis.