Objective : To study the pregnancy outcome with the use of letrozole in patients of unexplained infertility undergoing controlled ovarian hyperstimutation with intrauterine insemination. Materials & Methods : 27 patients of unexplained infertility attending the infertility clinic of Gynaecology Outpatient Department were enrolled in the study. They were administered letrozole 5 mg from day 3 to day 7 and subjected to follicular monitoring. Ovulation trigger with human chorionic gonadotrophin in a dose of 10,000 IU was given when one or more follicles > 16-18 mm diameter was found. A single intrauterine insemination using processed semen was performed 36 hours after ovulatory trigger.