We report the results of a double blind placebo controlled crossover randomized study of the calcium channel blocking agent diltiazem in the treatment of Raynaud's phenomenon. Our results showed a significant reduction in both frequency and duration of attacks of vasospasm in the hands. There was no detectable difference in response between patients with primary and those with secondary Raynaud's phenomenon. Our study supports the use of calcium channel blocking agents in the treatment of intermittent digital vasospasm.