OBJECTIVE: The objective was to assess the efficacy of double intrauterine insemination (IUI) over a single periovulatory IUI in patients undergoing controlled ovarian hyperstimulation with low-dose recombinant follicle stimulating hormone (rFSH) combined with human chorionic gonadotropin (HCG). STUDY DESIGN: Ninety-four infertile women were randomly assigned to three groups; in group A (38 patients, 47 cycles) a single IUI was performed 36 h after HCG administration combined with timed intercourse the day of HCG administration; within group B (43 patients, 48 cycles) IUI alone was performed 36 h after HCG administration; in group C (39 patients, 43 cycles) a double IUI 12 and 36 h after HCG administration was performed. RESULTS: The mean age and the causes of infertility were similar between the three groups. The number of follicles greater than 15 mm on the day of HCG administration and the overall dose of rFSH required per cycle was not significantly different among the groups. The pregnancy rate (PR) per cycle and per patient was 14.9% and 18.4% in group A, 10.4% and 11.6% in group B, 20.9% and 23.1% in group C, respectively. There was no statistically significant difference in PR among the three groups. CONCLUSION: In rFSH/HCG cycles, two IUIs performed 12 and 36 h after HCG administration do not significantly improve pregnancy rates over a single insemination performed 36 h after HCG administration combined with or without timed intercourse the day of HCG administration.