A double-blind, placebo-controlled, cross-over trial of nifedipine 10 mg three times daily for 6 weeks, in 10 patients with Raynaud's phenomenon secondary to systemic sclerosis, is reported. A significant reduction in the duration of attacks of Raynaud's phenomenon was observed. Nifedipine therapy also reduced the number and severity of attacks of Raynaud's phenomenon and the development of new digital ulcers, and increased the digital blood flow, but none of these changes was statistically significant. No alteration in red blood cell deformability or leukocyte chemiluminescence was observed during nifedipine treatment.