Nationwide prevalence and mortality rates in systemic lupus erythematosus (SLE) were estimated using a computer file of all hospital discharge records and cause of death statistics from 1972 to 1978. Age-specific and sex-specific prevalence rates obtained from 1976 to 1978 and mortality rates from 1972 to 1978. In December 1978 the prevalence of SLE was 28:100 000. The overall mortality rate was 4.7 per million person-years in 1972-78. Active lupus nephritis, vascular events and infections were the most frequent causes of death in SLE patients.