In 499 patients with advanced rectal carcinomas (infiltration at least into the muscularis propria), a prospective study of the factors influencing the occurrence of local recurrence was undertaken. The statistical analysis involved a multivariate procedure employing logistic regression. Local recurrence was observed in 20.6% of the patients. Statistically significant factors were found to be: (a) therapy-independent, tumor-specific factors, and (b) the surgical procedure. Among the former, lymphatic spread, the depth of infiltration and localization of the primary lesion above or below the peritoneal reflection were of importance. If, in low anterior resections, the distal margin of clearance does not exceed 3 cm (measured in the fresh, unstretched, surgical specimen, and corresponding to about 5 cm in situ), the incidence rate of local recurrence increases significantly. If, however, such a margin of clearance is adhered to, the results obtained equal those seen in abdominoperineal excision of the rectum. Therefore, in low anterior resection of advanced rectal carcinomas the concept of a distal margin of clearance of more than 3 cm in the fresh, unstretched, surgical specimen should be retained.