There is increasing body of evidence to suggest that sex hormones may be closely involved in the pathogenesis of autoimmune diseases in humans. In the present article we discuss heteroimmune response differences between males and females and the roles of gender and sex hormones in autoimmune diseases in various species. The general conclusions are the following. Androgens and perhaps progestogens may protect from autoimmune disease; however oestrogens seems to have a dualistic effect on the immune system. Is has been demonstrated that oestrogens suppress antigen-specific T-cell dependent immune reactions while enhance B-cell activities.