Several series have examined the influence of blood vessel invasion (BVI) by tumor on survival of patients with colorectal cancer; however, little data are available regarding its influence on patterns of failure. In an effort to determine the influence of BVI on the patterns of failure and survival in rectosigmoid and rectal cancer, a retrospective review of 168 patients who underwent potentially curative surgery at the New England Deaconess Hospital was performed. In patients who had tumors with extramural BVI, there was a significant decrease in five-year actuarial survival compared with patients who had tumors with intramural BVI or were BVI-negative (BVI-). When the intramural and extramural types of BVI were combined, no significant impact was noted on the patterns of failure or survival in patients with BVI+ versus those with BVI- tumors. In contrast, the presence of lymphatic vessel invasion was found to significantly decrease survival. By using a proportional hazards analysis, it was found that BVI was not an independent prognostic variable. Therefore, the use of BVI alone is not recommended for selecting patients with rectosigmoid and rectal cancer who may benefit from adjuvant therapy.