The role of radionuclide techniques in the investigation of thromboembolic disease has been re-evaluated. Forty-eight patients suspected of having embolic lung disease (PE) or deep venous thrombosis (DVT) were studied prospectively and investigated with radionuclide venography and ventilation/perfusion lung scintigraphy. Thirty-two also underwent contrast venography and peripheral 99Tcm-labelled red blood cell scintigraphy. Both radionuclide techniques were compared to each other and against the 'gold-standard'. The overall agreement and disagreement rates were 89 and 11% for radionuclide venography and 88 and 12% for radionuclide blood pool venography. The overall sensitivity and specificity were 90 and 73% for radionuclide venography and 88 and 82% for radionuclide blood pool venography. The blood pool technique did not perform better than radionuclide venography which was valuable in the detection of DVT and confirmation of PE. Radionuclide venography appears useful especially in patients suspected of having PE and DVT.