Since the male sterilization (vasectomy) has been performed on a large scale as an accepted family planning in Korea on 1980s and this, in turn, has been followed by an increase in the number of patients requesting vasovasostomy. We studies 1000 consecutive cases of vasovasostomy performed from January 1975 to July 1995 in Pusan National University Hospital. In this report, we are going to present serial studies of vasovasostomy through which we attempted to find out what factors are of impotence in influencing the successful outcome of vasovasostomy operation. We inquired the operative results data through the questionnaire and telephone interview with survey of medical records. A total of 259 cases was excluded due to the loss of follow-up. The overall patency and pregnancy rates of 741 cases were 86.9% and 51.1%, respectively. The age of man at the time of anastomosis ranged from 23 to 57 years old with an average of 34.9. The most frequent reason for requesting vasovasostomy was the desire to have more children (43.4%). The average obstructive interval was 60.6 months with range from 1 to 264 months. If the obstructive interval had been less than 5 years patency rate was 92.4% and pregnancy rate 64.8%, but 6 years or more 84.1% and 48.5% (p<0.01, p<0.01). Patency and pegnancy rates according to intraoperative vas fluid were 93.1% and 62.8% for presence and 83.7% and 53.1% for absence (p<0.01, p<0.05). Patency and pregnancy rates according to histologically proven sperm granuloma at vasectomy site were 87.7% and 49.2% for presence and 86.9% and 50.6% for absence (p>0.05, p<0.05). Patency and pregnancy rates were not significantly different between microscopic standard vasovasostomy (88.4%, 64.3%) and modified vasovasostomy (89.5%, 56.3%)(p>0.05, p>0.05). Both patency and pregnancy rates according to level of anastomosis were 89.8% and 59.8% in cases of straight vas and 91.5%, 60.1% in cases of convoluted vas (p>0.05, p>0.05). Patency and pregnancy rates according to the kind of suture materials were 91.5% and 56.2% for absorbable, 91.0% and 64.2% for non-absorbable and 93.3% and 53.3% for absorbable plus non-absorbable, respectively (p>0.05, p<0.05). Thus it is suggested that the important factor influencing the success rate of vasovasostomy is the interval of obstruction and vasal ooze with surgical skills.