In this paper, I focus on the effects of outsourcing on conditional labor demand elasticities. I begin by developing a model of outsourcing that formalizes this relationship. I show that the increased possibility of outsourcing (modeled as a decline in foreign intermediate input prices and an increase in the elasticity of substitution between foreign and domestic intermediate inputs) should increase labor demand elasticities. I also show that, a decline in the share of unskilled labor, due either to skill biased technological change or to movement of unskilled labor intensive stages abroad, can work in the opposite direction and reverse the increasing trend in elasticities. I then test the predictions of the model using the U.S. Census Bureau’s Longitudinal Research Database (LRD). The instrumental variable approach used in the estimation of labor demand equations is the main methodological contribution of this paper. I directly address the endogeneity of wages in the labor demand equation by using average nonmanufacturing wages for each location and year as an instrumental variable for the plant-level wages in the manufacturing sector. The results support the main predictions of my model. U.S. manufacturing plants operating in industries that heavily outsource experienced an increase in their conditional labor demand elasticities during the 1980-1992 period. After 1992 elasticities began to decrease in outsourcing industries. This finding is consistent with the model which suggests that a decline in the share of unskilled labor in total cost could result in such a decrease in labor demand elasticities, precisely when the level of outsourcing is high. Estimates at the two-digit industry level provide further evidence in support of the hypothesis that heavily outsourcing industries experience greater increases in their elasticities.