The clinical presentation, initial laboratory and renal biopsy findings, and subsequent clinical course were studied and compared in 128 children with Henoch-Schoenlein (HS) nephritis and in 206 children with IgA nephropathy. The clinical and pathological findings of the two conditions were similar. After a mean follow-up period of 5 years, 72 patients (56%) with HS nephritis and 67 (32%) with IgA nephropathy showed no demonstrable abnormality, 29 (23%) with HS nephritis and 103 (50%) with IgA nephropathy had minor urinary abnormalities, 7 (5%) with HS nephritis and 26 (13%) with IgA nephropathy had heavy proteinuria and/or hypertension, and 20 (16%) with HS nephritis and 10 (5%) with IgA nephropathy had developed chronic renal failure. A worse outcome was significantly associated with the more severe clinical presentations and more severe glomerular changes by light microscopy in HS nephritis, whereas there was no relationship between the severity of clinical presentation and glomerular changes and prognosis in IgA nephropathy. These findings suggest that HS nephritis is an acute disease and prognosis is associated with the severity of glomerular changes at onset, while IgA nephropathy is a chronic, slowly progressive glomerular disease.