We performed a randomized, double-blind, placebo-controlled, crossover study of the therapeutic efficacy of prazosin (1 mg t.i.d.) in 24 patients with Raynaud's phenomenon. Comparison of prazosin vs. placebo showed a moderate subjective improvement with a reduction of the daily number (P = 0.003) and duration (P = 0.02) of attacks. Patients showed a marked preference (P = 0.0002) for prazosin. Finger skin temperature and laser Doppler estimated finger skin blood flow, assessed during a standard finger cooling test, revealed a beneficial effect of prazosin (P = 0.0001 and P = 0.003, respectively). No differences in reaction to therapy could be found between patients with Raynaud's disease and secondary Raynaud's phenomenon. We conclude that prazosin is useful in the treatment of digital vasospastic disease, with an overall good response in two thirds of patients.