The incidence of deep-vein thrombosis was studied in 146 consecutive Korean patients who had a cementless total hip replacement with a porous-coated anatomic prosthesis. All of the patients had discontinued taking aspirin, aspirin-containing compounds, or other antiplatelet medications fourteen days before admission to the hospital for the operation. Deep-vein thrombosis was diagnosed by roentgenographic venography, and pulmonary embolism, by perfusion lung-scanning. There was an unusually low incidence (10 per cent) of deep-vein thrombosis in this series. In contrast to other reports, we did not identify a relationship between deep-vein thrombosis and so-called risk factors such as advanced age, number of venous valves (more than five) in the lower extremity, abnormal coagulation-assay data, certain diseases, or preoperative limitation of mobility. In addition, hypertension, blood group, surgical approach, and choice of cemented or cementless total hip replacement did not seem to affect the incidence of deep-vein thrombosis. There was a low incidence of deep-vein thrombosis in patients in whom obesity, prolonged immobilization postoperatively, varicose veins, and hyperlipemia were not factors.