The incidence and prevalence of systemic lupus erythematosus (SLE) in a well defined area in the Midlands was determined, by case ascertainment using multiple sources, during the period 1.5.89 to 30.4.90. This first such study of SLE in the UK showed incidence rates of 1.5/100,000/year for males and 6.5/100,000/year for females. The highest incidence was seen in age groups 40-49 and 50-59 years, with rates for females of 10.5 and 18.4/100,000/year respectively. Prevalence rates were 3.7/100,000/year for males and 45.4/100,000/year for females: SLE was found to be more prevalent amongst Afro-Caribbean groups. The socioeconomic status of the SLE patients was similar to the local study population, using social class by occupation and disadvantage by geographical area as indicators. Marked overlap between different sources of retrieval suggests that ascertainment of cases was high.