['To assess whether chronic renal impairment (CRI) and/or renal replacement therapy (RRT) in systemic lupus erythematosus (SLE) are associated with reduced extrarenal SLE activity.', 'This was a retrospective cohort analysis of patients with SLE who are followed at the University of Toronto Lupus Clinic. Patients with SLE were studied in 2 stages; chronic renal insufficiency (defined as a serum creatinine > 200 mumol/1 for > 6 months) and following the institution of dialysis therapy. Controls consisted of the next 2 age and sex matched patients in the clinic with a history of lupus nephritis who had not developed renal insufficiency. We assessed the flare rate (an increase in nonrenal SLEDAI > or = 1.0) for patients and controls in the first 12 months of followup at the clinic in each stage.', 'Twenty-one patients, 17 female and 4 male, were followed through 25 episodes of CRI or RRT as were 50 controls. In the CRI stage (n = 12), flares occurred in 8 (67%) within one year compared to 14 (58%) of 24 controls (p = NS). In the RRT stage (n = 13), flares occurred in 7 (54%) compared to 16 (62%) of 26 controls (p = NS). The magnitude as well as the characteristics of the flares did not differ between patients and controls in either stage.'] Is extrarenal disease activity in systemic lupus erythematosus suppressed by chronic renal insufficiency or renal replacement therapy?