Nine normotensive progressive systemic sclerosis patients with normal renal function underwent renal biopsy. Four specimens had prominent vascular abnormalities, two mild vascular abnormalities, and three were normal. Vascular deposits of C3 were present in all specimens. Plasma renin activity was elevated in three of four patients with prominent vascular abnormalities, one of two patients with mild vascular lesions, and none of two patients with normal biopsies. Plasma renin activity elevation in response to cold pressor testing in the four patients with prominent vascular lesions was 5.6 ng/ml · h compared to 0.55 ng/ml · h in those with mild or no lesions and 0.26 ng/ml · h in six control subjects. These data indicate that renal vascular lesions may be present in normotensive patients. Elevation or a substantial rise in plasma renin activity (1.8 ng/ml · h or greater) in response to cold pressor testing suggests preclinical renal involvement.