Background: Infertility treatment is important due to the high prevalence and destructive effects of psychological and social concerns of infertility. Intra Uterine Sperm Insemination (IUI) is a costeffective and noninvasive treatment method of infertility.Objective: The aim of this study was to examine the relationship between sperm count, sperm motility, women's age and IUI success.Methods: This analytical study was performed on 55 couples, with 63 treatment cycles, in Kosar infertility center, Qazvin during 2009-2010. Basic information on women's age and their husband’s occupation was obtained through questionnaires. Sperm count and sperm motility were determined according to the WHO criteria. Sperm were prepared by swim up method and were transferred to the uterus with a catheter. After two weeks, the pregnancy was confirmed by urinary b-HCG test.Data were analyzed by Chi-square and Fisher exact tests and P£0.05 was considered significant.Findings: The success rate was 9.5% per cycle of IUI. No significant difference was seen between the mean age of women in both successful and unsuccessful IUI groups. The relationship between the mean number of spermatozoa, the mean percentage of sperm progressive motility in the semen and pregnancy was not statistically significant.Conclusion: With regard to the results, women’s age and percentage of sperm progressive motility could not be used to predict the success rate of IUI, accurately.