Nineteen children and 160 adults with Crohn's disease were examined. The children had been under treatment between 1972 and 1974. There were 11 boys and 8 girls. Their main symptoms were general malaise, diarrhea, abdominal pains, anemia and weight loss. Clinical examination showed pallor, malnutrition, and abdominal tenderness on palpation. In 7 of 19 cases, rectosigmoidoscopy showed pathological changes. Radiologically, the most frequent site of the disease was observed to be in the ileocecal area. Since conservative therapy is associated with the risk of grave local and general complications, resection of the affected intestinal segment was the method of choice. Resection must be carried out through healthy tissues. Although the intestinal absorption of B12, fat and bile acids deteriorated after resection of the ileum, the general state of health of the patient improved. Body weight, serum albumin, serum iron concentration and the total iron binding capacity increased and the patient developed normally. Relapses occurred in 8 of the 19 cases. From the large number of adult patients who were studied, it could be shown that the risk of a relapse was greater in the ileal and ileocolic disease than in disease restricted to colon.