To determine the pathologic characteristics of colorectal cancer in the very old, a retrospective study of 947 consecutive Japanese patients aged > or =65 with 1,039 lesions were examined. Pathologic findings in the very old group (>85 years, n = 140) were compared with those in the younger groups; young-old group (65-74 years, n = 352) and middle-old group (75-84 years, n = 455). Although male:female ratio significantly decreased with advancing age, reaching 1:1.8 in the very old group, the relative odds of colorectal cancer in men were higher than that in women in all age groups. In the very old group, cancer of the proximal colon (proximal to the splenic flexure) accounted for 52% in women and 37% in men, being significantly higher than those in the younger groups. Proximal colonic cancers increased with advancing age in both genders. Higher proportions of poorly differentiated adenocarcinoma, mucinous carcinoma, cancer >5 cm in size, and protruding type cancer were present in the very old group, although these kinds of tumors typically occur in the proximal colon. The incidence of multiple cancers in the large intestine was not different among any age group (average, 8.6%). These results indicated that, even in the very old, colorectal cancers showed marked proximal excess, being explained by effect of both age and gender, and that the proximal shift may influence the proportion of histologic type and size of the tumor. These findings have important implications for screening and diagnosis of colorectal cancer in the elderly.