Diet plays no direct role in neutralizing the effects of the basic defect in cystic fibrosis, but it can prevent some of the acquired damage caused by complications. Adequate caloric intake provides the energy needed for exercise and cell metabolism, a strong diaphragm, normal cellular immunity, and a positive psychological outlook. Clinical management is aimed at achieving good nutrition. Patient education about nutrition and use of dietary supplements should be started immediately upon diagnosis. Careful clinical examinations and regular follow-up are necessary to detect complications that will interfere with good nutrition. Complications must be treated aggressively. Psychological and social stresses need to be recognized, and psychological referral may be necessary. The clinician's best tools to achieve these goals are the patient's dietary and gastrointestinal history, the anthropometric measurements taken at each office visit, regular patient assessment, and constant attention to detail in monitoring and charting the course of disease. Extraordinary measures, such as nighttime feedings by nasogastric or gastrostomy tube and intravenous hyperalimentation, may be necessary. For best results, these measures must be started before pulmonary complications threaten survival.