OBJECTIVES: Prospective, 3-year longitudinal dietary intakes of 25 prepubertal, pancreatic-insufficient children with cystic fibrosis (CF) and mild lung disease, and the intakes of 26 control children were compared, and relationships among energy intake, nutritional status, and pulmonary function were determined. STUDY DESIGN: Intakes from 3-day weighed food records were compared with CF recommendations, recommended dietary allowances (RDA), and the recommendations of the Third National Health and Nutrition Examination Survey (NHANES III). Energy and nutrient intakes were analyzed by repeated-measures analysis of variance. RESULTS: Children with CF consumed more energy than control children (p = 0.025) in terms of calories per day, percentage of RDA by age and by age and weight, energy adjusted for fat malabsorption, and percentage of NHANES III recommendations. Energy intake was similar between boys and girls with CF. The percentage of energy from fat was greater (p = 0.0004) in the CF group (3-year mean, 33%) than in the control group. Height and weight z scores declined in the CF group (p <0.05) with time. Vitamin and mineral intakes were generally adequate in the CF group. CONCLUSIONS: The children in this sample did not consume the CF recommended intakes of 120% RDA for energy or a high-fat (40% of energy) diet. Energy intakes may be insufficient in this group to meet requirements for optimal growth. (J PEDIATR 1996;129:119-29)