Administration of 4-methyl (6,7-b-tetrahydrobenzofurano) coumarin, 20 mg/kg/altemate day, for a period of 40 days caused degenerative changes in the testes of male rabbits. Inhibition of spermatogenesis was achieved at primary spermatocyte stage level. Total protein, sialic acid and glycogen contents of the testes, epididymis and seminal vesicle were significantly reduced while the testicular cholesterol was elevated in the 4-methyl coumarin treated animals. Serum cholesterol, phospholipid, triglyceride, nefa, were elevated. Antispermatogenic activity of 4-methyl coumarin is discussed.