We have evaluated the therapeutic effect of the calcium entry blocking agent nifedipine in Raynaud's phenomenon associated with connective tissue diseases and in idiopathic digital vasospasm. In a preliminary study 16 patients with a digital vasospasm that could be induced by hand-immersion in cold water (4 degrees C) were challenged a second time with cold water 1 and 6h after 20 mg oral nifedipine. Nifedipine provided an effective protection against this cold-induced vasospasm in 14 of the 16 patients. Thirty patients were included in a short-term ambulatory study: Raynaud's phenomenon was associated with progressive systemic sclerosis (PSS) in 10 patients, systemic lupus erythematosus (SLE) in five and rheumatoid arthritis (RA) in three; it was idiopathic (I) in 12 patients. Each patient received, in a double-blind manner and random order, on two consecutive weeks, nifedipine (20 mg three times daily) and placebo. Nifedipine proved to be effective: the mean number of digital vasospastic attacks per week decreased from 27.3 to 5.8 (P less than 0.01). The results in the SLE and RA groups were similar and were pooled. The improvement (in % decrease) was better in the idiopathic group (90.9) than in the SLE and RA group (78.6, P less than 0.02) and the PSS group (64.0, P less than 0.01).