Despite diffuse disease of the lungs (often with widespread inflammation or obliteration of blood vessels) in sarcoidosis, pulmonary hypertension is uncommon, occurring in 1% to 4% of cases. We report a case of sarcoidosis and severe pulmonary hypertension that, in striking contrast to other reports, occurred in the absence of obliterative pulmonary vascular disease. We therefore examined the possibility of whether an abnormality in pulmonary vascular tone might be a cause of the pulmonary hypertension. In pharmacologic studies, we demonstrated pulmonary vasodilatation and, in response to increased pulmonary blood flow, the elaboration of the pulmonary vasoconstricting eicosanoid, thromboxane.