Intrauterine insemination (IUI) is a fertility treatment that involves placing sperm inside a woman's uterus to facilitate fertilization. The goal of IUI is to increase the number of sperm that reach the fallopian tubes and subsequently increase the chance of fertilization. IUI is commonly used for unexplained infertility. It is also used for couples affected by mild endometriosis, problems with ovulation, mild male factor infertility and cervical factor infertility. Insemination is a reasonable initial treatment that should be utilized for a maximum of about 3 months in women who are ovulating (releasing eggs) on their own. It is reasonable to try IUI for longer in women with polycystic ovaries (PCOS) and lack of ovulation that have been given drugs to ovulate.