We examined the efficacy of induced vasodilation as a treatment of idiopathic Raynaud's disease. Eight persons with Raynaud's disease and seven normal persons each received 27 simultaneous pairings of hand immersion in warm water (43 degrees C) for 10 minutes with exposure of the whole body to cold (0 degrees C). A second group of seven normal persons and nine persons with Raynaud's disease received no treatments. All subjects had cold test exposures (0 degrees C) at the start and end of the study. Subjects with Raynaud's disease who received treatments showed significant increases in digital temperatures (2.2 degrees C) during the cold test compared with the values of untreated subjects with Raynaud's disease (p less than 0.05); normal subjects who had received treatments showed no difference from those who had not. Digital temperatures of subjects with Raynaud's disease after treatment increased to levels approaching those of normal subjects, although they showed lower digital temperatures during initial exposure to cold (p less than 0.01). This therapy offers a practical alternative to traditional treatments.