Intrauterine insemination (IUI) is used to treat unexplained infertility and male factor infertility. The male partner provides a semen specimen on the day that the female's egg is released. A laboratory procedure is then used to separate the active sperm from the inactive sperm and fluid. This procedure isolates the sperm cells from the seminal fluids. The "washed" sperm cells are then concentrated into a small volume and then placed inside the uterus painlessly using a tiny hollow tube attached to a small syringe containing the sperm.