Twenty cases of membranous glomerulonephritis have been diagnosed between 1978 and 1988 in children (13 girls, 7 boys) aged 4 to 15 years, observed for a 5.1 +/- 2.9 year period. The conditions of the diagnosis were: routine urinalysis in 10 cases, edema in eight, and the surveyance of a D-penicillamine treatment in two. All the patients had proteinuria (0.3 to 15 g/24 h) ranging to nephrotic syndrome in nine children. Microscopic hematuria was found in 16 children (80%). Elevated blood pressure was recorded in two cases at the time of diagnosis, and developed in two other cases during the follow-up. One child experienced renal failure at the onset of the disease. Most histological lesions consisted in stage II membranous glomerulonephritis. Immunofluorescence study (18 biopsies/20) always showed granulosus and intensive IgC deposits, associated with IgM and IgA deposits which were less marked; intensive extra-membranous C3 deposits were noted in 11 cases. As to the etiology, D-penicillamine was responsible for two cases (10%) and HBs antigen in one (5%); the nephropathy was considered as idiopathic in the 17 remaining cases (85%). Regarding the evolution: in eight cases (38%) proteinuria disappeared by 54 +/- 28 months; in 10 cases (55%), proteinuria persisted after 41 +/- 31 months; hematuria, which was present at onset, disappeared in most cases (13/17); in one case (5%), end-stage renal failure occurred within 3 years. The patient with initial renal failure has been last sight off.(ABSTRACT TRUNCATED AT 250 WORDS)