Abstract: It is known that human chorionic gonadotropin (hCG) elevates cAMP concentration in the ovaries of immature female rats and increases the weight of seminal vesicle of immature male rats. In the present paper, these two effects of hCG were used as indexes to examine the anti-hCG effect of ethane-1,2-dimethyl-sulfonate (EDS) and its derivatiVes. Results indicate that:(1) EDS (75～100 mg/kg), chloroethyl methane sulfonate (75～100 mg/kg) or bromoethyl methane sulfonate (25～50mg/kg) exhibited significant antagonistic action to hCG in both test models, while glycerol trimethane sulfonate (75～120 mg/kg) or propylene-1,2-dimethane sulfonate did not show any anti-hCG effect.(2) Ethyl-methane sulfonate (120 mg/kg) or β-phenyl-ethyl-methane sulfonate (120mg/kg) revealed suppressive effect on hCG in seminal vesicle weight test. However, at the same dosage, these two compounds did not show apparent anti-hCG action in cAMP concentration test.(3) n-Propyl-methane sulfonate (75～120 mg/kg)or isopropenyl-methiane sulfonate (120mg/kg) exhibited anti-hCG effect in seminal vesicle weight test.According to the data presented, the possible loci of action and the structureactivity relationship of EDS and its derivatives were discussed.