Objective-To determine the effectiveness of ovulation induction after laparoscopic treatment of endometriosis in an infertile population. Design-An observational prospective study in which infertility cases were treated with laparoscopic surgery was followed up (mean 11 months), either by treatment (ovulation induction) or no further treatment (expectant management) and the outcomes recorded. In both groups pregnancies were compared by Cox's regression survival model. Setting-Gazi University Hospital, Department of Obstetric and Gynecology, Ankara, Turkey. Patients-Infertile women with different stages of endometriosis who were treated by laparoscopic surgery, with a mean duration of infertility of 80.7 (+/-50 [SDI) months. Interventions-Patients were treated by cauterization of the foci, adhesiolysis, endometrioma stripping, and distal tubal reconstruction according to their lesions. Postoperatively, patients had either ovulation induction (clomiphene, hMG) therapy or no further treatment. Main Outcome Measure-Cumulative pregnancy rate of infertile women after laparoscopic treatment of endometriosis with or without ovulation induction. Results-A total of 36 out of 128 patients became pregnant after laparoscopy, with a 34% cumulative pregnancy rate. In the ovulation induction group, relative risk (chance) of pregnancy was 1.42 (1.02-2.05, 95% CI) when the duration of infertility was less than 5 years. In this lower risk group, the overall cumulative pregnancy rate was 46%-56% and 27% for the ovulation induction and expectant management groups, respectively. In the expectant management group, per cycle fecundity was 0.021, whereas it was 0.066 and 0.174 (p = 0.001) in the clomiphene citrate- and hMG-treated patients, respectively. Expectant management significantly increased the likelihood of pregnancy compared to ovulation induction in previous pregnancy, stage 1 or 2 endometriosis, and no male infertility groups (p = 0.04-0.009). Conclusion-After laparoscopic treatment of endometriosis, ovulation induction has a positive effect only if done with hMG and the duration of infertility was less than 5 years (P <.05).