Over the past 50 years, survival has improved in patients with systemic lupus erythematosus and associated nephritis. Yet, there are few long-term outcome studies in patients with well-defined nephropathy. We examined the outcome of 439 patients with lupus nephritis who were seen at the Mayo Clinic between 1964 and 1986 in whom renal biopsies were assessed using the World Health Organization (WHO) classification. There were 341 women and 98 men (mean +/- s.d., age 33.5 +/- 14 years); 200 (46%) patients were hypertensive and 249 (57%) had impaired renal function at renal biopsy. All WHO morphologic classes were represented and 339 (77%) patients had class III, IV and V (the more severe forms of nephritis). Follow-up averaged 10.2 years per patient. At last contact, 286 (65%) patients were alive and 153 (35%) were dead. Overall patient survival was 80%, 69% and 53% at 5, 10 and 20 years after biopsy that was significantly worse than expected survival (P < 0.001). Ten-year cumulative patient survival improved comparing earlier to more recent time spans: 64% in 231 patients seen during 1964-75; 76% in 2089 patients studied during 1976-86 (P = 0.03). Survival free of renal failure was 83%, 74% and 64% at 5, 10 and 20 years, and survival was unfavorably influenced by progressive WHO class, hypertension, impaired renal function, nephrotic range proteinuria, hypoalbuminemia and anemia. Multivariate analysis found impaired renal function, increased urine protein, anemia and younger age to be independent predictors of renal failure. WHO class was not a significant predictor when adjusted for these four factors. Cardiovascular events accounted for 48% of the known deaths and were equally distributed across all WHO classes, followed by infections, renal failure, malignancy, respiratory failure and gastrointestinal bleeding.(ABSTRACT TRUNCATED AT 250 WORDS)