This thesis analyzes three questions around the Heckscher- Ohlin (HO) predictions. The first one is related to trade impact on the increase of wage inequality in the United States, and presents results that are consistent with this argument when the distortion caused by unions of unskilled workers is taken into account. The second one studies the theoretical and empirical concerns related to the comparative advantages sources that are revealed by a country international trade. It is added two theoretical considerations to the literature: technological differences between countries and between periods. Based on this debate the comparative advantages sources are determined to Brazil, showing that this country is rich in unskilled workers, capital and land, but scarce in skilled workers. Finally, the impact of free international trade policies - occurred in the 90s - on the Brazilian labor market is evaluated, taking into account the technological changes. The tests elaborated are consistent with the HO predictions, and technological innovations present contrary effects to openness on labor market.