During a 9-year period 1,469 men who underwent microsurgical vasectomy reversal procedures were studied at 5 institutions. Of 1,247 men who had first-time procedures sperm were present in the semen in 865 of 1,012 men (86%) who had postoperative semen analyses, and pregnancy occurred in 421 of 810 couples (52%) for whom information regarding conception was available. Rates of patency (return of sperm to the semen) and pregnancy varied depending on the interval from the vasectomy until its reversal. If the interval had been less than 3 years patency was 97% and pregnancy 76%, 3 to 8 years 88% and 53%, 9 to 14 years 79% and 44% and 15 years or more 71% and 30%. The patency and pregnancy rates were no better after 2-layer microsurgical vasovasostomy than after modified 1-layer microsurgical procedures and they were statistically the same for all patients regardless of the surgeon. When sperm were absent from the intraoperative vas fluid bilaterally and the patient underwent bilateral vasovasostomy rather than vasoepididymostomy, patency occurred in 50 of 83 patients (60%) and pregnancy in 20 of 65 couples (31%). Neither presence nor absence of a sperm granuloma at the vasectomy site nor type of anesthesia affected results. Repeat microsurgical reversal procedures were less successful. A total of 222 repeat operations produced patency in 150 of 199 patients (75%) who had semen analyses and pregnancy was reported in 52 of 120 couples (43%).