To determine the incidence and significance of pulmonary vascular changes in scleroderma, all necropsy reports of patients with scleroderma who died at the Massachusetts General Hospital were analyzed and correlated with clinical data. The records of 30 such patients were available. Fourteen had moderate or marked abnormalities in the pulmonary arterial tree. Nine of these 14 patients had predominantly respiratory symptoms. The arterial changes consisted pathologically of intimal and medial hyperplasia affecting pulmonary arteries of all sizes. Of the eight patients with the most severe pathologic changes in the pulmonary arteries, five had slight or no interstitial fibrosis. Three of these five patients had rapidly progressive respiratory failure and severe pulmonary hypertension leading to death. Such cases form a distinct clinicopathologic entity of malignant pulmonary hypertension in scleroderma, comparable to the better recognized entity of malignant renal hypertension in scleroderma.