A Danish multicentre study was undertaken of the manifestations, infections, thrombotic events, survival and predictive factors of survival in 513 Danish patients with systemic lupus erythematosus (SLE) according to the 1982 classification criteria of the American College of Rheumatology. The mean duration of follow-up was 8.2 years from diagnosis and 12.8 years from first symptom. This paper describes the most common clinical and laboratory manifestations and their relationship to sex and age at the time of onset and diagnosis. Cluster analysis revealed three clinically defined clusters at the time of disease onset. Cluster 1 (57% of patients) consisted of relatively elderly patients without nephropathy or malar rash, but with a high prevalence of discoid lesions. Cluster 2 (18%) consisted of patients with nephropathy, a third of whom also developed serositis and lymphopenia. The patients of the third cluster (25%) all had malar rash and half were photosensitive. Follow-up showed that the patients of cluster 2 developed azotaemia, large proteinuria, arterial hypertension and myositis significantly more often than did the rest of the patients, but the mortality was not increased. The risk of developing renal end-stage disease was highest in men with early-onset disease.