Background: Controlled ovarian hyper stimulation and intrauterine insemination (IUI) cycle is an ideal protocol for some sub fertile patients. So, we decided to try this therapeutic protocol for the patients with unilateral tubal blockage diagnosed by hysterosalpingography (HSG).Objective: To evaluate the effect of unilateral tubal blockage diagnosed by HSG on cumulative pregnancy rate (CPR) of the stimulated IUI cycles.Materials and Methods: A cross-sectional analysis was performed between October 2006 and October 2009 in an academic reproductive endocrinology and infertility center. Two groups of patients undergoing stimulated IUI cycles were compared. Sixty-four infertile couples with unilateral tubal blockage diagnosed by HSG as the sole cause of infertility in the group (I), and two hundred couples with unexplained infertility in the group (II). The patients underwent 3 consecutive ovarian hyper stimulation (Clomiphen citrate and human menopausal gonadotropin) and IUI cycles. The main outcome measurements were the CPRs per patients for 3 consecutive stimulated IUI cycles.Results: Cycle characteristics were found to be homogenous between the both groups. CPRs were similar in group I (26.6%) and group II (28%) (p=0.87; OR=1.075; 95% CI: 0.57 -2.28)Conclusion: Unilateral tubal blockage (diagnosed on HSG) has no effect on success rate of stimulated IUI cycles, so COH and IUI could be recommended as the initial therapeutic protocol in these patients.