Deep vein thrombosis (DVT) of the lower extremities is not frequently encountered in Oriental patients. We investigated its aetiology and prognosis in 143 patients (65 males, 78 females), presenting to the National Taiwan University Hospital over 4.3 years, diagnosed by colour Doppler ultrasonography. Swelling and pain of the lower extremities were the most frequent presenting symptoms. The left femoropopliteal veins were more frequently involved than other parts of the lower extremities. In these patients, malignancy with or without intravenous catheterization was the most frequent cause (39 patients, 27%). Other common aetiologies included coagulopathy (29 patients, 20%), immobilization (24 patients, 17%) and catheter-related (13 patients, 9%). No definite aetiology could be determined in 37 patients (26%). During follow-up, 27 patients (19%) died, mostly with malignancy. Pulmonary embolism was noted in 16 patients and was not significantly directly related to death. Compared to similar studies in Caucasian patients, there were significant differences in the aetiology of DVT, with malignancy and coagulopathy more common in these Chinese patients.