Fifty-five patients with clinical signs of acute DVT were investigated with thermography, plethysmography and phlebography. A comparison between phlebography and thermography showed a diagnostic agreement of 84%. Thermography was found, however, to have a low reliability for the localization of acute thrombi and was therefore combined with plethysmography in an attempt to obtain better results in this respect. Compared to the invasive phlebography, the noninvasive combination of thermography and plethysmography adequately located acute DVT in 95% of the cases.