Effects of the β-methyl group at C-10 and some oxygen functions (= O, OH, OAc) at C-11, C- 17, and C-20 on the rates of hydrogenation of 3-oxo-4-ene steroids have been studied with palladium catalyst in pyridine or THF/HBr as solvent. In contrast to the hydrogenation in pyridine, the rate in THF/HBr was greatly depressed by the presence of 10β-methyl group. The reactivity of the steroids was enhanced by the oxygen functions, in particular, by 11, ...