Randomized. Patients were assigned to one of four treatment groups: slow release Nifedipine, a calcium channel blocker; pill placebo; temperature biofeedback; or electromyograph biofeedback from the frontalis muscle. The primary endpoint was reduction in number of vasospastic attacks. Other endpoints included: other measures of Raynaud's attacks including frequency, severity, duration, response to laboratory-based cold challenge, and quality of life.