Recurrent pregnancy loss (RPL) is one of the most common obstetrical complications. Multiple etiologies, such as endocrine, anatomic, genetic, hematological and immunological causes have been reported for this devastating disease. However, over half of the cases remain unexplained. Thrombotic/inflammatory processes are often observed at the maternal-fetal interface as the final pathological assault in many cases of RPL, including those of unexplained etiologies. In the present paper, cellular immune responses (T, natural killer [NK], natural killer-T [NKT], regulatory T [Treg] cells and their cytokines) and autoimmune abnormalities of women with RPL are reviewed. In addition, metabolic diseases and hematological conditions which often lead to thrombotic/inflammatory conditions are discussed in association with RPL. Finally, current therapeutic options for RPL are reviewed.