In the present study we assessed the frequency and characteristics of the main causes of morbidity and mortality in SLE during a 5-year period and analyzed the prognostic significance for morbidity and mortality of the main immunologic parameters used in clinical practice. We started in 1990 a multicenter study of 1,000 patients from 7 European countries. All had medical histories documented and underwent medical interview and routine general physical examination when entered in the study, and all were followed prospectively by the same physicians during the ensuing 5 years (1990-1995). Four hundred thirteen patients (41.3%) presented 1 or more episodes of arthritis, 264 (26.4%) had malar rash, 222 (22.2%) active nephropathy, 139 (13.9%) fever, 136 (13.6%) neurologic involvement, 132 (13.2%) Raynaud phenomenon, 129 (12.9%) serositis (pleuritis and/or pericarditis), 95 (9.5%) thrombocytopenia, and 72 (7.2%) thrombosis. Two hundred seventy patients (27%) presented infections, 113 (11.3%) hypertension, 75 (7.5%) osteoporosis, and 59 (5.9%) cytopenia due to immunosuppressive agents. Sixteen patients (1.6%) developed malignancies, with the most frequent primary localizations the uterus and the breast. Several immunologic parameters (anti-dsDNA or antiphospholipid antibodies) were found to have a predictive value for the development of SLE manifestations during the period of the study. Forty-five patients (4.5%) died; the most frequent causes of death were divided similarly among active SLE (28.9%), infections (28.9%), and thromboses (26.7%). A survival probability of 95% at 5 years was found. A lower survival probability (92%) was detected in those patients who presented at the beginning of the study with nephropathy.