In investigating the occurrence and clinical characteristics of diseases of the large intestine, particularly tumors, the number, distribution, and incidence of the lesions were compared between segments of the large intestine. If the distribution and incidence of lesions are correlated with the length or surface area of each segment, the incidence of lesions will be the same throughout the large intestine. If the lesions are unrelated to length or surface area, the factors that affect the occurrence of lesions must be determined and will be characteristic for each segment. However, the length and surface area of each segment of the large intestine and the ratios of each to both the total length and surface area of the large intestine are not clear. In this study the length and surface area of each segment of the large intestine were measured and calculated using the barium enema technique, and the incidence rates of cancer per unit length and surface area of each segment were determined and compared.