purpose: To compare disease activity in patients with systemic lupus erythematosus (SLE) (1) before and after the onset of end-stage renal failure and (2) during hemodialysis and continuous ambulatory peritoneal dialysis (CAPD). patients and methods: Records of 55 patients with SLE currently being treated with dialysis were reviewed. Disease activity was measured according to the SLE Disease Activity Index, event rates per 1,000 months' patient observation, and use of medication. results: In the majority of patients, deterioration of renal function was slowly progressive over more than 2 years. After the initiation of dialysis for end-stage renal failure, maximal extrarenal disease activity and use of medication decreased markedly, but event rates for specific nonrenal manifestations of lupus did not decrease. Overall survival with dialysis was 89% after 5 years. During dialysis no difference was found in disease activity and use of medication between treatment with either hemodialysis or CAPD. Thrombocytopenia and elevated levels of anti-double-stranded DNA, however, occurred more frequently during CAPD. conclusion: Patients with SLE have excellent survival rates with dialysis; their disease activity is diminished during dialysis but not abolished. No difference in survival or disease activity was found between patients undergoing hemodialysis or CAPD.