The fibrinogen uptake test has been used to detect deep vein thrombosis after total hip replacement in 90 patients. The upper third of the thigh in each leg was ignored and peripheral leg counting carried out distal to this. The results were directly compared with the findings of venography in the 170 legs of the 90 patients. There was a high false positive rate (30 per cent) with the fibrinogen uptake test which was associated with the presence of the knee joint effusion or varicose veins, but not with the site of operation. There was a low false negative rate (less than 5 per cent), and the fibrinogen uptake test, used in this way, may fail to detect a percentage of small thrombi in the wound area that are probably produced by the local trauma of operation. It is considered that the fibrinogen uptake test has a clinical use as a screening test for deep vein thrombosis after hip replacement, but venography is required in the interests of accuracy.