The effect of enalapril in the treatment of Raynaud's phenomenon was assessed in a prospective double-blind cross-over trial in 17 patients (nine primary Raynaud's, eight Raynaud's associated with scleroderma). Each patient received 20 mg enalapril daily and placebo for 3 weeks with a 2-week washout period in between. The severity and frequency of Raynaud's attacks were measured subjectively by a diary count and objectively by measurement of finger systolic pressure changes in response to cooling (cold challenge test). Enalapril was associated with a reduction in the frequency of Raynaud's attacks, especially in patients with primary Raynaud's, compared with placebo, but there was no effect on the cold challenge test. We conclude that enalapril, like other vasodilator drugs, helps the symptoms of Raynaud's phenomenon, especially in patients with idiopathic or primary disease.