The aim of this study was to evaluate the success rates of intrauterine insemination (IUI) in infertile women with unilateral proximal and distal tubal blockage. A total of 161 couples with unilateral tubal blockage and unexplained infertility were included. The primary outcome measure was the cumulative pregnancy rate (CPR). The CPRs after three cycles of IUI were 26.3% (10/38) in patients with unilateral tubal blockage, and 44.7% (55/123) in patients with unexplained infertility (p = 0.043). CPRs were similar in patients with proximal unilateral tubal blockage and unexplained infertility (38.1% vs 44.7%, respectively, p = 0.572). CPR was significantly lower in patients with distal unilateral tubal blockage than in patients with unexplained infertility (11.7% vs 44.7%, respectively, p = 0.01). In conclusion, IVF instead of IUI may be a more appropriate approach for distal unilateral tubal blockage patients.