['To analyze the effectiveness of pre-washing the intrauterine insemination catheters on IUI outcome.', 'Infertile couples (n=322) involved in a IUI program were included in the study. IUI indications were cervical factors, ovulation dysfunction, cryopreserved semen and unexplained infertility. Every other week for two years, IUI catheters were washed with culture medium prior to intrauterine sperm insemination.', 'Only the first IUI for each couple were analyzed. Washing the catheter, prior to use, resulted in a 49.7% increase in clinical pregnancy rate (22.0% vs 14.7% P<0.05). This result is observed with fresh sperm (15.7% vs 11.1%) and frozen-thawed sperm as well (31.1% vs 19.8%). The early pregnancy termination rate was similar in all groups.'] Does [ Pre-washing catheter dramatically improve the post intrauterine insemination pregnancy rate ]?