An autopsy case-control study of renal vascular histology and morphometry in systemic sclerosis (scleroderma) was performed. Thirty-five of 70 systemic sclerosis cases had renal tissue available for study: 26 had diffuse cutaneous involvement (9 with "renal crisis" and 17 without) and 9 had limited cutaneous disease (CREST syndrome [calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias]). Age-matched (within 10 years) and sex-matched controls with renal specimens were obtained. New sections were cut from tissue blocks, and morphometry was completed using a Zeiss Image Analyzer. Using analysis of variance, the intimal area (Ai) was significantly increased (intimal thickening) in small and medium-sized arteries of patients with diffuse scleroderma and in small arteries of CREST patients, compared with those in controls, while a decreased medial area (Am) was seen consistently in all groups. The proportion of the vessel wall occupied by intima (Ai:[Ai + Am]) was significantly greater in all vessel size groups in patients with diffuse scleroderma compared with that in controls. The percentage of luminal occlusion was greatest in patients with diffuse disease with renal crisis. These same patients had severe edematous and mucinous intimal thickening in small and medium vessels, often in association with fibrinoid necrosis. We conclude that renal vascular structural changes are an integral part of systemic sclerosis. However, the significant differences between diffuse scleroderma patients and CREST syndrome patients, for both intimal thickening and percentage of luminal occlusion, suggest that the arterial disease in these 2 patient subsets is distinctive.