CDT was epoxidized with t-butyl hydroperoxide in 1,2-dichloroethane over MO(CO)(6) as catalyst CDT/hydroperoxide (1:1-10:1) and catalyst/hydroperoxide (0.0001-0.001) mole ratios, temp. (70-110 degrees C) and by-products (t-BuOH and ECDD) were examd. to see how they affected the yield and rate of epoxidation. At 1:1 CDT/hydroperoxide mole ratio, ECDD yield was max at 76.9%, but selectivity was poor, similar to 50%. The ratio was optimum at 3:1. Conversion of CDT was max (32.2%) at 90 degrees C. At 110 degrees C, the hydroperoxide decompd. The catalyst/hydroperoxide ratio was optimum at 0.0005, but otherwise was a negligible factor Products inhibited the reaction, t-BuOH more than ECDD, presumably by complexation of the catalyst.