The ovarian hyperstimulation syndrome is a serious, and potentially life-threatening, complication of ovulation induction. Hitherto, there has been no reliable test which will predict patients who will subsequently develop ovarian hyperstimulation syndrome. Recently, evidences have accumulated concerning the interaction between the immune and reproductive systems which results from sharing certain lymphohaematopoietic cytokines and their receptors. Furthermore, several cytokines have been implicated in the prediction and pathophysiology of ovarian hyperstimulation syndrome. If this is true, it may be possible to modify the patients' immunological homeostasis by passive immunization with intravenous immunoglobulin (IVIg) and thus to prevent ovarian hyperstimulation syndrome.