The feasibility of a gradational step test for the assessment of work capacity was investigated. A device was constructed on which the level of a stepping platform could be raised between 2.0 and 50 cm as subjects continued work at a prescribed stepping rate. Two test procedures applicable to individuals who vary in their state of health from that of a chronically ill patient to a trained athlete are described. Sixty men performed experiments to establish the minute-by-minute metabolic costs of the work in the two tests. The oxygen expenditures ranged from 12.9 ± 1.2 to 40.8 ± 3.5 ml/min per kg in the 30/min step test and from 10.7 ± 1.1 to 28.8 ± 1.3 ml/min per kg in the 24/min step test. The procedures are well suited for measuring various physiological parameters during stepping and for establishing physiological working limits. The oxygen costs of the “negative” and “positive” work components in stepping were determined. The cost of negative work was approximately one-third of the positive work. An equation was derived for predicting the metabolic costs of stepping at various rates and platform levels. Comparisons of predicted and measured oxygen intake values for the 30-step and 24-step tests approximated one another at all levels of energy expenditure. energy expenditure stepping; cardiorespiratory responses to exercise; work in stepping; negative work; positive work; physical fitness tests Submitted on August 7, 1964