It had been previously thought that protein excretion in hypertensive nephrosclerosis was less than 0.5 to 1.0 g/24 h. Furthermore, it was believed that proteinuria in the nephrotic range associated with hypertension was probably due to primary renal disease, malignant hypertension, renal artery stenosis, or pheochromocytoma. We report eight patients with biopsy-proven hypertensive nephropathy and heavy proteinuria in the absence of malignant hypertension or renal artery stenosis. The 24-hour protein excretion ranged from 2.7 to 4.3 g. All patients had renal insufficiency, with serum creatinine ranging from 2.0 (176.8) to 7.8 mg/dL (689.5 mumol/L). Renal function worsened in most patients during the follow-up period despite adequate control of the hypertension, and three patients had to be started on hemodialysis. Three patients died during the follow-up period. We conclude that hypertensive nephrosclerosis must be included in the differential diagnosis of marked proteinuria in patients with essential hypertension and that heavy proteinuria, along with renal insufficiency, are poor prognostic indicators in such patients.