The nutritional status of critically ill, pulmonary-compromised patients is often overlooked. Patients seen in intensive care units have greater nutritional demands than are experienced during simple starvation. Pulmonary complications of malnutrition can lead to respiratory failure, unsuccessful weaning from the ventilator, and death. Simple techniques for the assessment of nutritional status are available. The provision of adequate calories and micronutrients must be based on sound, currently held concepts. The various complications of nutritional support that relate to the respiratory system should be well known by those working with the ventilator-dependent patient. While many aspects of nutritional support remain unresolved, a current recommendation is the accurate calculation of energy and protein needs for the prevention of overfeeding. The respiratory quotient determinations of a group of hypermetabolic patients have revealed that at least 50% of nonprotein calories should be provided in the form of fat so as to decrease carbon dioxide production, norep-inephrine excretion, and oxygen consumption. In addition, future nutritional formu-las will incorporate recently acquired research data that support an increase in the concentration of branched-chain amino acids. (Barrocas A, Tretola R, Alonso A Jr. Nutrition and the Critically Ill Pulmonary Patient. Respir Care 1983;28:50-61.