From 1983 to 1985, 214 patients with rectal carcinoma were assessed for the conformation rate of the rectal examination to the gross findings of the extent of perirectal infiltration in the resected specimens. It was found that the conventional classification of the extent of rectal infiltration by rectal examination, 1/4, 1/3, 2/4, 3/4 and 4/4 of the circumference, had only a conformation rate of 32.7% to the gross findings. According to the classification of 1/4 or less and more, the conformation rate could reach 93%. It was also found that the extent of perirectal infiltration, being closely related to the regional lymph node metastasis and the depth of invasion, was only demonstrated by this latter classification, which was not shown in the conventional classification. Hence, it is suggested that the rectal examination implying the extent of perirectal infiltration by simply classified into two groups: equal to or less than 1/4 and more than 1/4 of the circumference of the rectal wall.