This monograph presents in detail a study performed with healthy young women as subjects, designed to determine the degree in which gaseous metabolism is increased in the erect versus the recumbent position during the postabsorptive state. The posture of each subject was analyzed, and the relative metabolic cost for different standing positions was compared statistically. The data indicate that less energy is required when support is based on ligamentous bracing of joints than when the position is maintained through muscular balance. In other words, the position assumed with fatigue is more economical physiologically than is the posture of readiness for response, usually accepted as the desirable standing position. The difference of expenditure of energy between these two postures, though statistically significant, is not appreciable when compared with the cost of other factors which continuously are in operation in an active subject.