It has been reported that the risk of thromboembolism after general surgery in Chinese is negligible, thus, prophylaxis has not been used. This study examined the incidence in the high risk subgroup of patients undergoing colorectal operations. In a two-year retrospective review, 35 rectum resections for cancer, 72 colon resections for cancer, and 22 colon resections for benign disease were analysed. The clinical incidence of deep vein thrombosis (DVT) in patients with malignancy was 4.7% (5/107). None of the patients with benign disease had DVT. Three of the five patients with DVT had pulmonary embolism, of which one died. Rectal surgery incurred a higher risk (11.4%) compared to colonic resection (1.4%) (p = 0.038). Postoperative wound infection was an important predisposing factor (p = 0.027). In view of these findings, a prospective trial has been planned to further evaluate the need for prophylaxis in selected high risk patients.