The survival advantage of a pronounced lymphocytic infiltration within and around the primary tumor and some hyperplastic reactions in the regional lymph nodes in specimens of colorectal cancer has been reported in many studies. However, none of these studies allowed the grade of these immunomorphological reactivities to compete with more traditional prognostic variables, using the proportional hazard models. In this study the survival rates of 219 patients who underwent operation for rectal cancer were analyzed statistically according to sex, age, tumor site, type of operation, histology, nuclear grade, p-TNM stage of disease and to the following immunomorphological parameters: lymphocytic infiltration (LI) within and around the primary tumor, paracortical activity (PCA), cortical activity (CA) and sinus histiocytosis (SH) of the regional lymph nodes. The presence of an evident local and regional immune reactivity was significantly related to a less advanced stage of disease and better differentiated tumor. The multivariate survival analysis (Cox model) identified LI, PCA and SH and p-TNM stage as independent prognostic factors. Survival within each stage progressively increased in presence of one or more favourable immunomorphologic features. These results indicate that an adequate prospective evaluation of LI, PCA and SH should improve our ability to assess prognosis in rectal cancer and, therefore, allow a more rational utilization of adjuvant therapy.