The measurement of basal metabolic rate (BMR) is an important element in the estimation of energy requirements in man. Based on a survey of 2822 BMR measurements conducted in the tropics, a series of new predictive equations to estimate BMR in tropical peoples is presented. These new equations based on bodyweight show that the current FAO/WHO/UNU predictive equations overestimate BMR of peoples living in the tropics by an average of 8 per cent, and by up to 11.5 per cent for males over 30 years old. These differences were significant over between 65 and 100 per cent of the normal bodyweight range found in our data, for both males and females over 10 years old. However, for younger ages, 3-10 years, the FAO/WHO/UNU equations predicted BMR quite accurately. The inclusion of height made no significant difference to the predictive equation. Although caution must be exercised in interpreting these results, it is concluded that the lower BMR in the tropics appears to be a general and genuine phenomenon in adults. Further discussion of energy requirements in tropical peoples must consider these observed deviations in BMR from the FAO/WHO/UNU predictive equations.