As interest in systemic lupus erythematosus (SLE) research has increased, it has become apparent that knowledge about SLE epidemiology has lagged behind. The most fundamental aspect of epidemiology of any disease is determining the disease's incidence and prevalence rates. The reported rates for SLE vary greatly. This is due partly to the inherent disparities of the disease; however, great variation also exists in study methodology. Understanding these differences and defining ideal approaches will advance our current understanding of the literature and future efforts. Well-designed epidemiologic studies of SLE also can help further our understanding in several related research areas.