Total energy expenditure was measured in a cohort of 33 normal, full term infants at 12 weeks of age using the doubly labelled water technique. These data were related to Quetelet's index and the sum of the triceps and subscapular skinfold measurements at 9 months and 2 years of age. Correlation coefficients were used to determine the relationship between total energy expenditure and later indices of body composition. Total energy expenditure was expressed as kcal/kg per day; kcal/kg0.5 per day (in order to negate the effect of body weight) and kcal/kg fat free mass per day (in order to take into account body composition). Using this approach there was no relationship between the level of total energy expenditure at 12 weeks of age and later indices of body fatness. The highest correlation coefficient being 0.09 (n = 33, P greater than 0.10). These findings are contrary to recent reports that a reduced total energy expenditure is related to the development of obesity in certain selected groups of individuals.