We evaluated nutritional status, pulmonary impairment, nutritional intake, and fat absorption in 73 cystic fibrosis (CF) patients to identify the primary factor(s) influencing growth. In general, the growth pattern in our patients was satisfactory since 60/73 were not underweight. When caloric intake is greater than or equal to 95% of RDA, wasting does not occur regardless of the degree of malabsorption, dietary fat content, or lung involvement. In the group of patients who consume less than the RDA, underweight is related to the severity of pulmonary disease; indeed, 11/13 underweight patients have a chest x-ray score over 15. Steatorrhea is well controlled in most patients; only 11 of 73 show a fat excretion greater than 25% of fat intake. The daily number of capsules of Pancrease varies from 4 to 57. The amount of Pancrease to be given was individualized to meet each patient's requirements using fat balance studies to determine the necessary daily Pancrease dose, then distributing the total dose in proportion to the fat content of each meal.