Seminal fructose, citric acid and acid phosphatase were estimated from 23 healthy males before vasectomy and three months later. Each subject had children and the men volunteered for sterilization because other possibilities of contraception were inapplicable. Vasectomy was performed under local anesthesia in the conventional manner. Semen of all patients was azoospermic three months after vasectomy. In this study, the amounts of seminal fructose and citric acid were significantly higher after vasectomy than before operation. The activity of seminal acid phosphatase was a little less, but the difference was not significant. The increase of seminal fructose and citric acid could be explained by the lack of spermatozoa, which normally use them into their metabolism.