To evaluate the factors affecting the incidence of ectopic pregnancy following tubal reversal, the clinical characteristics of ectopic pregnancy group (N=28)and intrauterine pregnancy group (N=316)were compared in 344 cases of pregnancy following tubal reversal using microsurgical technique at the Department of Obstetrics and Gynecolgy from July 1980 to May 1989. We found no significant relationship between the incidence of ectopic pregnancy and the duration of sterilization. Although the incidence rate (11.2%) of ectopic pregnancy following laparoscopic cautery appeared to be the highest among tubal sterilization methods, none showed statistically significant differences. There was a fourfold difference in the incidence rate of ectopic pregnancy between post-reversal tubal length less than 7cm (12.7%)and greater than 7cm (3.5%). The mean interval from tubal reversal to conception was 15.7months in ectopic pregnancy group, and 9. 3months in intrauterine pregnancy group, the difference reaching statistical significance. While most(80%)of the pregnancies were achieved within the first 12months following tubal reversal in intrauterine pregnancy group, 50% of the pregnancies occured in the same period, and the cumulative pregnancy rate is related in a linear fashion to the duration after reversal in ectopic pregnancy group. The incidence rate of ectopic pregnancy was found to be higher after cornual-ampullary anastomosis and cornual-isthmic anastomosis.