Before effective treatment for reproductive failure can be instituted, the cause of the failure must be determined. A search of PubMed was made to identify the published data regarding diagnosis and treatment of reproductive failure. Results were compared with the frequency of antiphospholipid antibodies (APA) in 2995 women with histories of unexplained infertility, recurrent implantation failure, recurrent pregnancy loss, and fertile women. In addition, pregnancy outcomes among 442 women experiencing reproductive failure and elevated NK cell activity after treatment with intravenous immunoglobulin (IVIg) (N = 242) or intralipids (N = 200) were compared. The prevalence of APA was the same among women with the diagnosis of unexplained infertility, recurrent implantation failure, and recurrent miscarriage. Heparin and aspirin are successful in the treatment of elevated APA among women with recurrent miscarriage but not with recurrent implantation failure. IVIg has been successful in the treatment of recurrent miscarriage and recurrent implantation failure among women with elevated APA and/or NK cell activity. When the pregnancy outcomes of women with a history of reproductive failure and elevated NK cell cytotoxicity treated with intralipid were compared with women treated with IVIg, no differences were seen. Immunotherapy for treatment of reproductive failure enhances live birth but only in those women displaying abnormal immunologic risk factors.