The gene responsible for the lpr mutation in MRL mice that are prone to systemic lupus erythematosus has been shown to encode the apoptosis-inducing Fas antigen, thus pointing to control of apoptosis as a major regulatory mechanism in autoimmunity. In the non-obese diabetic mouse model for insulin-dependent diabetes, four non-MHC-linked loci have been localized in the murine genome that were found to be associated with successive stages of the disease. These findings should soon have a major impact on our understanding of human autoimmune diseases.