From 1969 to 1979, 169 patients with two or more renal angiograms for renovascular disease (85 atherosclerotic, 75 fibrous, 9 atherosclerotic and fibrous) were reviewed in an attempt to characterize progression of disease and to determine clinical markers of progression. Progression of renal artery atherosclerosis was observed in 37 patients (44 per cent); progression to complete occlusion was observed in 14 patients (16 per cent). In the 66 patients with medial fibroplasia, progression was observed in 22 patients (33 per cent). Serial serum creatinine measurements in conjunction with measurements of kidney size may be used as markers of progressive atherosclerotic renovascular disease. These clinical markers did not represent progressive disease for individuals with medial fibroplasia.