Although noninvasive techniques have been extensively evaluated in the diagnosis of deep vein thrombosis (DVT), few data exist about the role of computerized impedance plethysmography (CIP) in the diagnosis of delayed DVT after surgery, when patients are at home and the risk of DVT is still high. The aim of this study was to evaluate the reliability of CIP in the diagnosis of proximal and distal delayed DVT in both symptomatic and asymptomatic patients who had undergone elective total hip replacement (THR). Bilateral CIP of lower limbs was performed in 61 patients on days 5, 9, 15 and 45 after THR; for comparison, ascending phlebography was performed on days 45 after THR in all patients on the operated limb or on the limb with positive results on CIP. The overall rate of DVT diagnosed by phlebography was 16.3% (10/61). The sensitivity and specificity of CIP for all DVT were 20% and 98%, respectively, while the accuracy was 85%. The results were not influenced by the presence of symptoms or signs of the lower limbs. Similar results were obtained when considering proximal DVT only. In conclusion, the low sensitivity of computerized impedance plethysmography means that it cannot be used in screening for delayed deep vein thrombosis after total hip replacement, in both symptomatic and asymptomatic patients. However, because of its high specificity, when the results of computerized impedance plethysmography are positive phlebography should be performed to confirm the diagnosis of deep vein thrombosis.