Renal biopsies were performed on 13 patients treated with captopril. In 4 patients findings indicated an early stage of membranous glomerulopathy (MGP). In the other patients electron microscopy showed scanty small subepithelial deposits and immunofluorescence revealed a patchy granular pattern along the glomerular basement membrane. One of the 4 patients with MGP presented with nephrotic syndrome and another with serum-sickness-like syndrome. None of the other patients, including 2 with MGP, had proteinuria or deterioration of renal function. Thus captopril may be associated with the development of immune-complex glomerulopathy.