Cystic fibrosis as a specific disease entity has been known to be associated with malnutrition for almost half a century. The importance of the malnutrition in the disease process remains unknown, as does much information about specific nutritional deficiencies in CF. Supplements for children with CF should include extra energy as fat or carbohydrate, a form of linoleic acid that can be absorbed, hydrolyzed protein, fat-soluble vitamins with vitamins A and E in a water emulsion, vitamin B12, probably B vitamins and vitamin C, and trace minerals. Routine measurements of nutritional status, particularly in children with growth failure, should be made at regular intervals and should include a three-day diet record and a simultaneous 72-hour stool fat determination. If fat malabsorption is not controlled by pancreatic enzymes, the use of antacids or cimetidine should be considered. The true role of nutrition in patients with CF will not be known until the appropriate studies are completed.