This review highlights recent studies that investigate causes and treatments for recurrent pregnancy loss. Generally the causes of recurrent pregnancy loss are classified as genetic, endocrinologic, anatomic, immunologic, microbiologic, and environmental. The majority of recent work has focused on potential autoimmune and alloimmune causes; however, controversy still exists over appropriate testing and treatment. Reports have investigated the potential associations between autoimmune factors (antithyroid antibodies and antiphospholipid antibodies) and alloimmune factors (natural killer cells, cytotoxic T cells, and embryotoxic factors) and recurrent pregnancy loss. Increasingly, clinical reports are suggesting intravenous immunoglobulin as a potential treatment for these immunologic problems. Several lines of investigation have suggested certain hypercoagulable states as causative of recurrent pregnancy loss. New studies relating recurrent pregnancy loss to endocrinologic aberrations (hyperprolactinemia and hyperandrogenism) as well as social/environmental factors (stress, caffeine use, tobacco use, human immunodeficiency virus, and history of induced abortion) have been made. A summary of proposed evaluation and treatment options is presented.