Renal function studies were performed in 18 subjects in different stages of Henoch-Schönlein glomerulonephritis (HS GN). Nine children were serially investigated, and nine adolescents or young adults, who were considered to have clinically recovered, were investigated only once, 10.5-14 years after the onset. Inulin and PAH clearance, as well as sodium excretion, were determined during hydropenia (HP) and 3% volume expansion (VE) with isotonic saline. In most patients in the former group a renal biopsy was performed during the first investigation and again one year later. The early disturbances in renal function resembled those we have found in other types of GN. The GFR was normal during HP or after VE in most cases one year after the onset. The natriuretic response to VE was decreased in most patients initially, and this was found to persist in half of the patients 2-3 years after the onset. Pathological urinalyses then indicated disturbances in the renal handling of sodium. A reduced capacity to excrete sodium, however, did not seem to be of prognostic significance since all patients, except one who developed renal insufficiency and hypertension, had normal urinalyses and blood pressure six years after the onset. This study provides no evidence that subjects with previous HS GN will later develop impaired renal function or be predisposed to hypertension.