The purpose of this study was to comparatively investigate the energy expenditure of jumping on sand and on a firm surface. Eight male university volleyball players were recruited in this study and performed 3 sets of 10 repetitive jumps on sand (the S condition), and also on a force platform (the F condition). The subjects jumped every two seconds during a set, and the interval between sets was 20 seconds. The subjects performed each jump on sand with maximal exertion while in the F condition they jumped as high as they did on sand. The oxygen requirement for jumping was defined as the total oxygen uptake consecutively measured between the first set of jumps and the point that oxygen uptake recovers to the resting value, and the energy expenditure was calculated. The jump height in the S condition was equivalent to 64.0±4.4% of the height in the maximal jump on the firm surface. The oxygen requirement was 7.39±0.33 liters in S condition and 6.24±0.69 liters in the F condition, and the energy expenditure was 37.0±1.64 kcal and 31.2±3.46 kcal respectively. The differences in the two counter values were both statistically significant (p<0.01). The energy expenditure of jumping in the S condition was equivalent to 119.4±10.1% of the one in the F condition, which ratio was less than in walking and close to in running.