The onset and course of 108 children with systemic lupus erythematosus have been analysed. There were more black patients than one would expect from hospital population statistics. There was a greater preponderance of boys with onset of the disease at less than 12 years of age and there is a large number of familial cases. Major signs and symptoms differed from those observed in adults only in the greater degree of reticuloendothelial involvement and in a possibly greater propensity for children to change renal biopsy category. Diffuse proliferative renal lesions remain a major contributor to death both in children and in adults, but the importance of the extrarenal mortality factors plus the greater proportion of male deaths is emphasized.