OBJECTIVE: To evaluate the effects of 10 minutes of bed rest after intrauterine insemination (IUI) on the pregnancy rate. DESIGN: Prospective randomized study. SETTING: University teaching hospital. PATIENT(S): One hundred sixteen couples with unexplained infertility. INTERVENTION(S): Patients were prospectively randomized either to immediate mobilization after IUI (group I) or to remain in a supine position for 10 minutes after the procedure (group II). MAIN OUTCOME MEASURE(S): Cumulative pregnancy rate. RESULT(S): Ninety-five couples were included in the analysis. Group I consisted of 40 couples (90 cycles), and group II consisted of 55 couples (120 cycles). The pregnancy rate per couple in group I (4 of 40 [10%]) was significantly lower than in group II (16 of 55 [29%]). The pregnancy rate per cycle in group I (4.4%) was also lower than in group II (13. 3%). With use of life-table analysis, the cumulative probability of pregnancy in group II was significantly higher than in group I. CONCLUSION(S): A 10-minute interval of bed rest after IUI has a positive effect on the pregnancy rate. We recommend that mandatory bed rest for 10 minutes after IUI should be adopted into a standard practice.