Reversible vasospasm has been hypothesized to underlie the development of pulmonary hypertension in patients with CREST. Drugs that prevent arterial spasm have been used to treat pulmonary hypertension with variable results. The disparate pulmonary hemodynamic responses to calcium channel blockade reported herein suggest that CREST patients with mild pulmonary hypertension may have a component of reversible vasospasm responsive to vasodilator therapy, whereas patients with moderate to severe pulmonary hypertension may have fixed vessel lesions precluding a satisfactory response to calcium channel blockade.