Two cases of nephrotic syndrome and biopsy-proved membranous glomerulopathy (membranous glomerulonephritis) were encountered during captopril treatment of 53 hypertensive subjects in our institution. Both patients had impaired renal function before treatment and were treated with 600 mg per day. Discontinuation of captopril led to transient partial remission of proteinuria but was followed by a recurrent, fluctuating course over one year later. Repeat biopsies, eight and 12 months after discontinuation of the drug, demonstrated persistent subepithelial deposits in the glomerular basement membrane. There has been a decline in glomerular filtration rate since discontinuation of the drug, apparently due to arterionephrosclerosis. These studies suggest that glomerular basement membrane deposits in captopril-associated membranous glomerulonephritis are not readily reversible and may be associated with persistent proteinuria, contrary to some previous reports.