Factors influencing pregnancy rates in intrauterine insemination cycles. 
To identify the predictors of pregnancy rate (PR) among women undergoing intrauterine insemination (IUI) cycles.  Two hundred thirty-two women undergoing 255 IUI cycles were retrospectively evaluated according to clinical and semen characteristics in terms of PRs.  The overall PR was 9.4%.  The PR was 7.9% in the primary infertility group, whereas the rate was 21.4% in the secondary infertility group (p < 0.05).  The pregnancy rate was 3.1% for 1 preovulatory follicle, 9.3% for 2 follicles, 16.9% for 3 and 23.1% for 4 (p < 0.05).  The PR increased in accordance with the total motile sperm count before sperm preparation (p > 0.05); however, the PR was significantly higher in sperm morphology of >4% (according to Kruger criteria) than in the < or = 4% group (6.7% vs. 22.2%, respectively; p = 0.003).  Using binary logistic regression analysis, the number of preovulatory follicles and the percentage of normal sperm morphology in processed sperm had the maximum power to predict the PR following IUI.  Other than clinical and laboratory characteristics, only the number of preovulatory follicles and the percentage of normal sperm morphology in processed sperm can be used in the prediction of a favorable IUI outcome.