A respiration trial system using a ventilated flow-through method with a face mask was developed at Khon Kaen Animal Nutrition Research Center, Khon Kaen, Thailand in order to study energy metabolism in cattle. It is composed of four components: 1) main air flow component, 2) air sampling component, 3) gas analysis component and 4) data record and calculation component. The programs for data logger and calculation were written in Q-basic for IBM AT/PC-compatible computers. The recovery rate of the whole system was examined by using nitrogen and carbon dioxide gases. The overall average of the recovery rate was 93.3% with small standard deviations, i.e. 0.8-1.7% depending on the methods of examination of the rate. As the system is less costly for establishment than that with a hood or a chamber, it could be suitable for conducting studies on energy metabolism of ruminants in developing countries