Carcinoma of the large bowel is rare in persons under the age of 30, and generally presents with advanced stages of disease. From 1964 to 1984, 30 patients presented with nonfamilial large bowel malignancies. Seventeen patients were male, and 13 female (age range, 8-25 years). In 15 patients the primary was in the right transverse colon. In 26 patients the lesion was above the peritoneal reflection. Classification by Dukes' staging demonstrated Stage B in 3 patients, Stage C in 7 patients, and Stage D in 20 patients. Twenty-five patients had a mucinous variety of adenocarcinoma. Surgery at initial laparotomy consisted of biopsy (10 patients), palliative segmental resection (7 patients) and complete resection (13 patients; survival in each of these groups ranged from 1 to 15 months (median, 6 months), 6 to 36 months (median, 8 months) and 7 months to 14 years (median, 6 months), respectively. The only long-term survivors are three patients who had complete resection, two of whom are surviving free of disease after 5 and 15 years, respectively. Common sites of abdominal recurrence were the omentum (6 patients) and ovaries (7 patients). All patients received chemotherapy. In 16 of 24 evaluable patients, responses lasting 3 to 18 months were observed. Five patients also received radiation therapy. Follow-up of these patients included computed tomographic scans, ultrasound, and determination of carcinoembryonic antigen (CEA) levels. The CEA level in 9 of 23 patients did not correspond with the presence of either residual disease or progression of disease. Chemotherapy combined with a second-look surgical procedure in selected cases may improve the proportion of patients surviving and the duration of survival.