The aim of the presented study is to determine the effect of different sperm parameters on the pregnancy rate of intrauterine insemination (IUI) cycles in women with favourable fertility characteristics treated for infertility. Medical records of 212 infertile couples who had undergone a total of 253 cycles were reviewed retrospectively. Inclusion criteria for women were age <35 years, antral follicle count >5, FSH <15 IU/ml, and at least one patent tube documented by HSG or laparoscopy. Clinical pregnancy rates were achieved as 15.8% per cycle, and 18.8% per couple. Woman's age, partner's age, total number of motile sperm (TMS) and motility, significantly influenced pregnancy rate. Pregnancy rate was the highest when women were aged <25 and TMS >10 x 10(6). Partner's age significantly affected the pregnancy rate per cycle in women aged <30 years and TMS >10 x 10(6). Woman's age (OR: 5.4 95% CI: 1.2-24.3) and TMS (OR: 0.06 95% CI: 0.003-0.89) were predictor variables as regards to pregnancy. Pregnancy rate was the highest in IUI cycles when woman was <25 years old, TMS was >10 x 10(6), and morphology was 44%. Male age was found to be another determining factor for IUI success, even if they had a normal spermiogram.