The heart rate response to submaximal treadmill work been calculated using the heart rates and oxygen intakes obtained from normally nourished and undernourished adult male subjects during a maximal oxygen consumption test. Increased severity of malnutrition was associated with an increased heart rate response to the same submaximal work loads. The response was observed to decrease during a period of high protein dietary repletion of the most severely malnourished subjects. The data suggest the possibility of developing a submaximal work test for use in the field to provide physiological data to supplement anthropometric and biochemical information used to assess the nutritional status of populations.