Raynaud's phenomenon is a common, paroxysmal acrosyndrome, affecting about 4% of the general population. Most of the time it is a purely functional condition: Raynaud's disease. However, in rare cases, there is an organic cause and it is then known as Raynaud's phenomenon. In view of its prevalence, a simple, atraumatic, low cost and reliable work-up should be performed to guide diagnosis. This is based on the findings of clinical examination, capillaroscopy, antinuclear factor antibody tests and X ray of chest and hands. Only a few cases will require more specialised investigation with arteriography and autoimmune studies. The commonest causes are arterial and connective tissue diseases, especially scleroderma. However, occupational hazards, toxic and iatrogenic drug-induced aetiologies should not be overlooked. With the exception of patients who have a curable underlying disease, most cases require vasodilator therapy, the keystone of which over the last decade has been the calcium channel blockers. Only patients who are severely handicapped by their acrosyndrome should be given drug therapy.