All residents of Rochester, Minn., with a diagnosis of cancer of the colon or rectum during the 30‐year period, 1940 through 1969, were identified from the records of the Mayo Clinic and the other resources in the Rochester epidemiologic central file. The medical records and microscopic slides on these patients were reviewed, and 439 met the necessary residency and diagnostic criteria. Adjusted average annual incidence rates per 100,000 for the entire time period for cancer of the colon were 33.0 for males and 24.6 for females and for rectal cancer, 16.3 for males and 13.7 for females. Age‐specific incidence rates increase progressively with age for cancer in both sites. Age‐adjusted rates for both colon and rectal cancer were consistently higher for males than for females in the three decades studied. However, for both sites, the male predominance appeared only in those patients more than 60 years of age. In this study, we were unable to demonstrate significant increases in incidence rates in either sex for cancer of the colon or rectum over the 30‐year period.

No abstract