The results of a study carried out on 90 subjects exposed to vibratory trauma of the hand-arm compared to a non-risk control group of 54 subjects are reported. All subjects underwent a medical and neurological examination and Doppler ultrasound of the upper limbs, plethysmography of the hands, electromyography of the bilateral median nerve area and T.T.T. (Thermal Threshold Tester) evaluation of the thermal threshold, were performed. Workers exposed to risks show a higher threshold for hot/cold sensitivity compared to those not exposed. This increase is earlier compared to the onset of vascular and neurophysiological changes detected by plethysmography, Doppler ultrasound and electromyography. Thermal threshold evaluation by T.T.T. would seem to be a useful test for monitoring workers exposed to vibrations.