Using the results of randomized and controlled studies, it was assessed whether there is still a place for intra-uterine insemination (IUI), with or without controlled ovarian hyperstimulation (COH), as a treatment for male subfertility. It is concluded that, in the case of a moderate to severe semen defect, well-timed IUI should be applied in natural cycles only, because COH does not further improve treatment outcome. In contrast, in the case of a mild semen defect, the present evidence indicates that COH improves the probability of conception. If COH is applied, stimulation should be mild in order to prevent multiple pregnancies and the ovarian hyperstimulation syndrome.