Raynaud's phenomenon (RP) is a common vascular disorder characterized by a recurrent transient vasospasm of the fingers and toes on exposure to cold or with emotional stress. Clinical criteria are used to distinguish patients with primary or idiopathic RP (formely Raynaud's disease) from those with secondary RP (formely Raynaud's syndrome). They include history, general physical examination, capillaroscopy, test for antinuclear antibody and erythrocyte sedimentation rate. More specific exams may be needed in selective cases. Excluding RP of occupational origin, the most common cause of secondary RP is a connective tissue disease (particularly scleroderma). RP may precede other clinical symptoms by several years, but most patients with RP will not progress to systemic disease. Nevertheless, primary RP may cause significant disability. We review the pathophysiology and clinical criteria of the disorder. Unfortunately, management of PR is still empirical and largely supportive.