A high energy intake, compensating for malabsorption, and the energy cost of lung disease, lung infections, and the underlying metabolic abnormality, is required to ensure normal growth in patients with cystic fibrosis. This goal can be readily achieved by adherence to a high quantity, normally balanced diet (with 40% of the energy as triglycerides of long-chain fatty acids). In contrast, this goal cannot be reached in the majority of patients adhering to low-fat and thus low-energy-containing diets, which almost inevitably lead to malnutrition with wasting and stunting. The prevention of malnutrition may well have considerably enhanced the prognosis of patients at one clinic. Further work is needed to define the interrelationship of nutrition and lung disease, and to define the appropriate nutrient requirements induced by the lung disease per se, recurrent infections, and the underlying disease process.