One hundred and fifty-two patients who underwent abdominoperineal resection for cancer of the rectum and rectosigmoid are reviewed. Six physicians were selected to predict which of these patients would have a local recurrence. All information available at the end of the operation was duplicated and submitted to the observers. None of the physicians was able to predict local recurrence significantly better than random. There were 31 local recurrences, i.e. an incidence of 20-4 per cent. Low level of tumour in the rectum, local spread into perirectal fat or serosa, lymph node involvement and age below 60 years at time of operation were the only factors that were statistically related to local recurrence. The strategy for careful follow-up of patients at risk is outlined and a plea is made for a controlled trial of postoperative radiotherapy.