The etiological mechanism of the vasospastic component in the Vibration Syndrome has been studied in 99 subjects working with vibrating tools and 33 healthy controls. They were exposed to vibration, noise and body cooling. Finger—pulse plethysmography revealed strong vasospasms during simultaneous vibration exposure, particularly at frequencies from 80 to 125 Hz, and significantly more often in subjects than in the controls. Body cooling and exposure to loud noise potentiated the vasospasms produced by vibration. Contralateral muscle work generally caused vasodilatation of the finger vessels, but simultaneous vibration exposure could inhibit this dilatation or cause constriction. The occurrence of vasoconstriction was correlated with an index of the severity of vibration—induced white finger (VWF). The findings are compatible with the idea that sensory vibra tion receptors contribute to VWF through over—excitation of the Pacinian corpuscles, which produce reactions in vasculature by a reflex linkage with the sympathetic nervous system.