An experiment system is described which will permit quantitative physiological studies in 8-14 kg adult monkeys during future space flight opportunities such as the NASA Shuttle. The system comprises a fiberglass pod containing a comfortable restraint couch for the animal. The pod is divided into upper and lower halves. When the monkey occupies the couch, a rubber belly-band forms a gas seal between the upper and lower portions of the animal. The upper-pod ventilating air stream monitored for PO2, PCO2, PN2 and PH2O to permit continuous metabolic gas-exchange measurements for computation of metabolic energy expenditure. The lower pod is lined with ashless filter paper for excreta collection and entrapment of liquid urine, and is ventilated separately. At the end of experimental periods of 1 to 7 days, all excreta plus the filter paper are removed for chemical analysis. The lower-pod ventilating gas ports also allow application of lower-body negative pressure to test cardiovascular competency when desired. The upper pod is provided with automatic food pellet and drinking water dispensers for quantitative measurement of nutrient intake. Balance assessment of the following elements can be made: N, Ca, P, Mg, K, Na, Cl, S and Fe. Animals have been kept in continuous restraint in the system for as long as 30 days without apparent ill effects.