Four male volunteers served as subjects to examine the metabolic and ventilatory cost of both positive and negative lifting tasks as compared to bicycle ergometry. In different experiments, four boxes weighing 0.91, 6.82, 22.73, and 36.36 kg were lifted up to or down from a height of 60 cm at rates as high as 70 lifts/min for periods of 4 min. The data were then compared to those obtained from bicycling at a rate of 50 rpm at work loads up to 1,500 kmp/min. Work at any given box weight had a substantially higher oxygen and ventilatory cost than similar levels of work on the bicycle ergometer. The reason for these differences appeared to lie in the energy cost of moving parts of the body. When the weight of the boxes was low, there was little difference between the oxygen cost of positive and negative work, but as the weight of the boxes increased, the expected physiological differences in positive and negative work was established.