In order to investigate the reported antiobesity action of dehydroepiandrosterone (DHEA), a complete energy balance was made on four groups of mice. Group A was fed the standard Purina diet, group B the same diet to which DHEA was added (0.3%), group C the Purina diet supplemented with palatable high fat food (meat spread), and group D the same diet as group C, to which DHEA was added. Food intake which was larger in groups C and D, was not altered by DHEA treatment. Body weight gain which was comparable for groups A and C, was significantly reduced in the two groups receiving DHEA. The resulting reduced food efficiency caused by DHEA was completely explained by body fat utilization. It was also found that the weight and the protein content of the interscapular brown adipose tissue (BAT) were increased by DHEA treatment suggesting, because of the great thermogenic capacity of this tissue in mice, that it may have been involved in causing the observed reduction in food efficiency. It is also proposed that the action of DHEA may be related to the activation of other tissues such as the liver and muscles. Further investigations are needed to verify this possibility.