The mean incidence of colorectal carcinoma in persons under age 40 in Sweden is 1.74/100,000/year. Over a 30-year period, 1950 through 1979, 1061 patients with colorectal carcinoma were seen, 48 of whom where under age 40 (21 to 39 years) and in this study were compared with older patients. Carcinoma was superimposed upon ulcerative colitis in 18 patients. All patients treated for palliation died within two years. Curability rate. 67 per cent, and the proportion of Dukes' A lesions were the same as in older patients, whereas young patients had fewer B and more C lesions. Five-year survival was 33 per cent overall and 50 per cent in curable cases, not different from the rates in older patients (33 and 47 per cent). Five-year survival was 100 per cent in stage A, 50 per cent in stage B, and 33 per cent in stage C. The age factor had no impact upon survival, and colitic origin of a carcinoma did not decrease survival more than did carcinoma itself. It is concluded that colorectal carcinoma in patients under age 40 differs in no respect from the disease in older patients.