More than 300 patients undergoing microscopic vasovasostomy have been carefully studied in an effort to determine the factors which affect the recovery of fertility after an accurate microscopic reanastomosis. The over-all pregnancy rate in an unselected group of early patients was 71%. Recovery of fertility correlated with the return of normal sperm counts and with the quality of seminal fluid in the vas deferens on the testicular side of the obstruction at the time of vasovasostomy. The three most important factors influencing return of fertility after vasovasostomy are (1) a meticulous microscopic technique for reconnection, (2) the duration of time the vas deferens has been obstructed, and (3) the presence of absence of a sperm granuloma at the site of the vasectomy, venting the long-term pressure buildup which otherwise would occur. The presence of a sperm granuloma at the vasectomy site generally ensured the presence of good quality sperm in the vas fluid at the time of vasovasostomy and the recovery of a good sperm count postoperatively. If all three of these factors are favorable, vasectomy should be reversible for most patients.