Radionuclide venography and contrast venography were performed in 47 limbs of 35 patients, and the findings were compared with respect to their location and characteristics. Positive radionuclide venogram findings were area of decreased radioactivity flow corresponding to the region of thrombosis, abnormal collateral flows, and radioactivity stasis below the lesion. A delayed clearance of radioactivity alone in the calf did not indicate venous thrombosis. The overall concordance between radionuclide venography and contrast venography was 89%. The result indicates that radionuclide venography, while technically simple, is a reliable test for the detection of venous thrombosis in patients with signs and symptoms of deep-vein thrombosis.