Intrauterine insemination (IUI) with or without ovarian stimulation is a common treatment for infertility. Despite its popularity, the effectiveness of IUI treatment is not consistent, and the role of IUI and in vitro fertilization (IVF) treatment in practice protocols has not been clarified.Medline searches were done by individual topics (utilization, procedures, effectiveness of partner but not donor IUI and related endocrine issues). Effectiveness of IUI was evaluated in relevant randomized controlled trials, using meta-analysis and meta-regression where necessary.Stimulated IUI is ineffective in male infertility and the effect on other diagnoses is small. With clomiphene citrate and IUI, the most common IUI protocol, pregnancy rates average 7% per cycle. FSH ovarian stimulation and IUI treatment is only modestly better than observation only with pregnancy rate 12% per cycle but multiple birth rates averaging 13%. Mildly stimulated (1-2 follicles) cycles might reduce the cost and multiple birth rates but may require more cycles of treatment. Prevention of premature luteinizing hormone surges and luteal phase support do not appear to be major requirements in IUI cycles.IUI treatment requires ovarian stimulation to achieve modest results, but the high multiple pregnancy rates mean that it is no more than a poor substitute for IVF treatment. More trials are needed on IUI treatment with mild stimulation and on the order of IUI and other treatments.