Transcutaneous nerve stimulation (TENS) has been described as resulting in vasodilatation. The effect of 2 Hz TENS of the right hand during forty-five minutes on skin temperature and plethysmography of the third digit of both hands and feet and on transcutaneous oxygen tension (TcpO2) of the right hand was compared with that of a control study using indifferent stimulation of the iliopsoas region in 8 patients with primary Raynaud's phenomenon. After TENS a slight increase in skin temperature of both hands was found, while plethysmographic amplitude was increased in the contralateral hand only. No changes in TcpO2 occurred. The authors conclude that the observed small effects of TENS are of no clinical value in primary Raynaud's phenomenon.