Considerations in selecting a postvasectomy semen examination regimen.

The criteria for declaring a vasectomized man sterile have been the subject of debate for many years, yet most suggested regimens differ. The problem lies in the remaining unanswered physiologic questions of such a fundamental nature as to frustrate attempts to formulate a regimen based strictly on medical considerations. The rates of disappearance of sperm following vasectomy vary considerably among men. The physiologic basis for these variations are herein discussed for the first time. At present, regimens reflect, for the most part, social considerations, according to the values and perceptions of the individual physician. The problems raised by postvasectomy residual sperm and current formulation of regimens are described.