Proteinuria is well described in atherosclerotic renovascular disease (ARVD), but the prevalence is unknown, and the pathogenesis may vary between patients. Substantial proteinuria (> 2 g/day) however, would be regarded by many as atypical of ARVD. We studied 94 patients (52 male) with ARVD, median age 67 years (range 49-87). Digital subtraction angiography was performed on all patients. Protein was assayed in 24-h urine samples and GFR derived using the Cockroft-Gault formula. Forty-nine patients (52%) had proteinuria < 0.5 g/24 h. Proteinuria increased with worsening renal function. Biopsies from seven non-diabetic patients with substantial proteinuria showed: minimal changes (1); glomerular sclerosis with marked ischaemic changes (3); focal glomerulosclerosis (2); and athero-emboli (1). Proteinuria, rather than being indicative of other pathology, is often a marker of severity of parenchymal disorder in atherosclerotic nephropathy, which itself is the major determinant of renal dysfunction in patients with ARVD.