1. Measurements of oxygen consumption (V O2 ) and carbon dioxide production (V CO2 ) can be used to calculate energy expenditure. Such data are useful in the nutritional management of a variety of pathological conditions. 2. This study is an evaluation in vitro and in vivo of the mating of a canopy and a Beckman metabolic measurement cart 1 (MMC). The canopy allows for the collection of expired gases without facial attachments. 3. Studies in vitro demonstrated the necessity of calibrating the CO 2 analyser at the concentrations used in such a system (0.50-0.80% CO 2 ). Measurements of V o2 were within +12% to −8% of predicted values, and when calibrated at 0.50% and 0.75% CO 2 , measurements of Vco 2 were within +2% and −7% of predicted values. 4. The studies in vivo revealed that V O2 and Vco 2 were within ± 11% of the values obtained by using a canopy-spirometer-computer system. 5. The MMC plus canopy may provide an alternative method for the clinical measurement of Vo 2 and Vco 2 , especially in subjects unable to tolerate a tight-fitting mask for prolonged periods.