Between 1950 and 1978, 1,228 patients were operated upon by one of us for carcinoma of the rectum. Symptom duration data were available for 1,081 patients. Forty-five per cent of the patients had symptoms preoperatively for less than three months, 22 per cent for three to six months, 15 per cent for six to 12 months and 18 per cent for 12 months or longer. The frequency of major symptoms did not differ significantly with increasing symptom duration. Symptom duration was not related to sex, age, tumor site within the rectum or tumor stage distribution. The proportion of curative to palliative operative procedures performed was unrelated to the duration of symptoms. The cancer specific survival rate was better for the total patient series and for those treated by curative resection if symptoms had been present for 12 months or longer compared with those of less than three months' duration, p = 0.001 and p = 0.01, respectively. Survival prospects were also better for patients with symptoms of less than six months' duration compared with those of six months or longer, p = 0.01 and p = 0.04, respectively. These results indicate that earlier diagnosis during the symptomatic period of carcinoma of the rectum cannot be expected to improve cancer specific survival rates. They direct attention to the importance of preclinical diagnosis.