Eighty-seven colorectal carcinomas were studied histologically with special reference to grade of tumor, reactions of stromal tissue, and the morphology of regional lymph nodes. A special search was focused on the morphologic manifestations of possible host factors. The most interesting findings were: 1) nuclear grade of the tumor correlated with five-year survival; 2) the content of tumor-derived mucus was not a prognostic determinant; 3) the intensities of stromal lymphocyte and mast-cell reactions correlated with survival; 4) an active lymph-node paracortical area was almost incompatible with the appearance of nodal metastases.