Unexplained infertility is a multifactorial disorder of reproduction. This review examines the potential contribution of decreased uterine perfusion, obscure luteal phase defect, intrinsic endometrial factor ovum captor inhibitor, microscopic endometriosis, and psychologic factors for the cause of unexplained infertility. Although specific therapy for unexplained infertility does not exist and treatment-independent pregnancy frequently occurs in this group of patients, many couples pursue treatment. In vitro fertilization, gamete intrafallopian transfer, zygote intrafallopian transfer, superovulation with intrauterine insemination, and direct intraperitoneal inseminations are several treatment options reported to be successful. However, a randomized prospective study using a uniform diagnostic assessment, strict entry criteria, identical ovulation-induction schemes, and semen-processing protocols is lacking to determine which patients will be most appropriately treated with each procedure and which is more effective. Unexplained infertility is not and should not be considered a permanent state. These couples should be considered to be subfertile rather than infertile.