Of 668 Rochester, Minnesota residents with colon or rectal cancer diagnosed from 1940 through 1979, 400 (60%) were operated on for cure and had a known disease stage. The influence of patient sex, age, and decade of diagnosis, disease stage, grade, site, and size, and the presence of obstruction or perforation were examined as prognostic factors for death, death from colorectal cancer, and cancer recurrence. In this population-based inception cohort, overall survival was independently associated with male sex (P = 0.0002), older age (P less than 0.001), and more advanced disease stage (P less than 0.001). Death due to colon cancer, on the other hand, was associated with disease stage (P less than 0.0001), more advanced grade (P = 0.016), and the presence of obstruction (P = 0.003). One hundred seven (27%) patients had a recurrence of their colon cancer. Seventy-one percent of recurrences were evident within the first 2 years and 91% by 5 years. Recurrence was associated with disease stage (P less than 0.0001), grade (P = 0.006), and the presence of perforation (P = 0.012).