Nutritional status was evaluated in 50 medical admissions to a pediatric ICU. All patients were evaluated within 48 h of admission; none had chronic organ failure or malignancies. Nutritional assessment included weight/50th percentile weight for length, length/50th percentile length for age, triceps skinfold thickness, and midarm muscle circumference. Acute protein-energy malnutrition (PEM) occurred in 16% of all children. Chronic PEM also occurred in 16%. The nutrient stores of fat and somatic protein were deficient in 18 and 20% of all children. Acute PEM and deficient somatic protein stores were more frequent in children less than 2 years (p less than 0.05). These findings indicate that malnutrition and nutrient store deficiencies are common early in the course of critical illnesses in children, especially in those less than 2 years of age. However, the findings do not indicate if the severity of illness was the cause or effect of poor nutritional status.