Preoperative pharmaco-angiography using prostaglandin E1 was performed in 62 patients with colorectal cancer. The diagnostic significance of angiography for the prospect of invasion was evaluated comparing with operative and histological findings. The relationships between the histological incidence of extramural venous invasion, the incidence of liver metastasis and the angiographic extent of invasion were analyzed. Mesenteric vessels were classified into the following 3 groups for the angiographic evaluation. Group A: proximal to marginal vessels, marginal vessels and the proximal portion of the vasa recta Group B: the mid portion of the vasa recta Group C: the terminal portion of the vasa recta Angiographic abnormalities in Group A vessels were considered to correspond to a histological depth of serosa or more, abnormalities in Group B vessels to serosa or subserosa, abnormalities in Group C vessels to muscularis propria, and no abnormalities to submucosa or mucosa. According to these criteria, the evidence of extramural invasion could be diagnosed exactly on the basis of angiographic abnormalities in Group A or B vessels. Extramural venous invasion was histologically detected in 18 cases and 13 of them showed angiographic abnormalities in Group A vessels among 60 patients. Including cases found in post operative periods, 14 cases of liver metastasis were presented among 62 patients. Angiographic abnormalities were found in 11 of them in Group A vessels. Therefore it is thought that there is a high risk of liver metastasis in cases with angiographic abnormalities in Group A vessels. Preoperative angiography is useful in prospecting the invasive depth and in assessing the risk of liver metastasis of colorectal cancer.