Studies that present prevalence rates for Raynaud's phenomenon show great variation. Figures range from a few to more than 20%. In this study, 508 patients who attended their general practitioner filled in a questionnaire dealing with symptoms of Raynaud's phenomenon. When strict criteria (cold digits, numbness and at least a biphasic discolouration) were applied, prevalence was 0.5% in males and 2.9% in females. When a monophasic white discolouration was included, prevalence rates increased by 5.4% in males and by 7.5% in females. The respective percentages became 10.4% and 21.2% when subjects with cold digits and at least a monophasic white or blue discolouration were included. Complaints of cold digits were present in 22.7% of the males and in 35% of the females. We conclude that a great deal of the variation in prevalence of Raynaud's phenomenon can be explained by differences in its definition.