OBJECTIVE--To assess the effects of perioperative blood transfusion on cancer related survival and infective complications after radical operations for colorectal cancer. DESIGN--Retrospective study. SETTING--District hospital in Sweden. SUBJECTS--217 patients who fulfilled the criteria for inclusion, out of 392 consecutive patients operated on for colorectal cancer between 1975 and 1979. MAIN OUTCOME MEASURES--Morbidity and cancer related mortality depending on whether blood was transfused and, if so, how much. RESULTS--Dukes' stage (p