We retrospectively reviewed all patients with a final diagnosis of deep venous thrombosis (DVT) treated at Linkou Chang Gung Memorial Hospital between 1989 and 1995. There were a total of 245 patients with a mean age of 58 years (males 56 and females 59), ranging from 11 to 89 years. The ratio of left to right leg involvement was 2.4 to 1 (166 to 71), however, the right leg was more likely to lead to an acute pulmonary embolism, with a ratio of 3.0 to 1 (9/ 71 to 7/166 patients). Among these patients, 16.3% (40) had cancer. The most frequently involved system was the GI system (16). Adenocarcinoma proved the most common type of malignancy 62.5% (25/40). From this analysis, we found the left leg had a higher likelihood of thrombosis but a DVT of the right leg was more frequently associated with an acute pulmonary embolism. As with previous reports there was a strong relationship between cancer and DVT and the development of a deep venous thrombosis requiring a search for an underlying malignancy in those patients with an unexplained DVT.