Comparative studies of intestinal absorption utilizing test meals of I131-labeled neutral fat and fatty acid, administered on different occasions to the same individual, were performed in 10 patients with cystic fibrosis of the pancreas and in 13 control children. The results are compared with those previously obtained and reported in various groups of adults. Two of the patients with cystic fibrosis had normal tryptic activity in the duodenal aspirate. The experimental data in the two patients with cystic fibrosis and normal tryptic activity of the duodenal contents are presented, but no conclusions are drawn therefrom. This series will have to be expanded before theories regarding underlying disturbances can be advanced. All of the eight patients with cystic fibrosis and pancreatic achylia showed impairment of intestinal absorption of neutral fat, and to a lesser extent, of fatty acid. While the former result was expected, the impaired absorption of fatty acids was not, and is at variance with results in adults with acquired pancreatic deficiency. The hypothesis is advanced that an intestinal factor other than lack of pancreatic enzymes may be partially responsible for the defect in absorption in cystic fibrosis of the pancreas.