Eighty-three children with Henoch-Schoenlein nephritis were studied to establish the prognostic significance of the glomerular changes. After a mean follow-up period of 6 years, 44 patients had no demonstrable abnormality, 21 had minor urinary abnormalities, 8 had heavy proteinuria and/or hypertension, and 10 had either died or developed chronic renal failure. Patients presenting with hypertension and/or acute renal insufficiency were more likely to develop chronic renal failure than those with milder presentations. A poor outcome was found to correlate with (1) crescents and segmental lesions affecting a high proportion of glomeruli, (2) the presence of subepithelial electron-dense deposits and (3) the finding of extracellular "lead shot" microparticles. While the clinical presentation is not a good means of predicting the outcome, an acute nephritic onset nevertheless appears to be the best available indication for renal biopsy, which should include both light and electron microscopy in order to increase the precision of prognostication.