DNA content and cell proliferation were studied retrospectively in 125 patients presenting from 1974-1981 with rectal adenocarcinoma. The presence of DNA aneuploidy or a high level of cell proliferation were associated with a poor prognosis and when combined were the best predictor of survival after Dukes's stage excluding all other pathological assessments investigated. High cell turnover was significantly associated with an infiltrative pattern of growth, an observation that might explain the poorer prognosis of this pattern in rectal adenocarcinomas.