Deep vein thrombosis (DVT) is a common medical problem requiring early diagnosis and treatment in order to prevent serious sequelae. Currently available diagnostic acids are suboptimal, since they are either invasive (phlebography), insensitive (ultrasound), or slow (125I-fibrinogen uptake test). The 99Tcm-plasmin test was compared with the 125I-fibrinogen uptake test. The results were concordant in 38 of 40 cases studied (11 concordant positive and 27 concordant negative); a significant correlation (p < 0.05) was found. In a further 20 patients, the 99Tcm-plasmin uptake test was compared with X-ray contrast phlebography. In this series, 12 patients presented with concordant negative results, five patients with concordant positive results and three patients with a positive 99Tcm-plasmin uptake test in the presence of a negative phlebogram. Of these three cases, two presented with clinical evidence of pulmonary embolism and positive perfusion/ventilation lung scans. 99Tcm-plasmin appears to have the potential for early and rapid screening of deep-vein thrombosis 15 minutes after intravenous injection. The test is safe, quick, economic and easy to perform.