International variations in capital utilization as a result of operations are a significant but neglected characteristic of the world economy. In this paper we introduce endogenous capital utilization into the Heckscher-Ohlin model and we show that: if workers differ internationally in their willingness to work the abnormal hours associated with higher levels of capital utilization, the factor-price equalization theorem will no longer be valid, nor will technology and endowments be the sole determinants of comparative advantage.