Systemic involvement and spectrum of autoantibodies were evaluated in 91 patients presenting with Raynaud's phenomenon. Decreased pulmonary diffusing capacity was observed in 23 percent, esophageal hypomotility in 14 percent and renal involvement in 5 percent of the patients, all without clinical symptoms. Arthralgia or a history of arthritis was present in 27 percent and skin abnormalities in 30 percent. Extent of systemic involvement was correlated with the severity of Raynaud's phenomenon, as measured by photoelectric plethysmography (r = 0.38; p < 0.01). In addition, both the variety of different autoantibodies in the serum of individual patients and the titer of antinuclear antibodies were positively correlated with the number of affected organ systems (r = 0.63; p < 0.01 and r = 0.65; p < 0.01, respectively). Raynaud's phenomenon is an important clinical sign of asymptomatic systemic disease. Measurements of its severity and serologic parameters are helpful in predicting the extent of systemic involvement.