In this paper, we estimate mark-ups with plant level production data for Argentina from a structural model of cost-minimizing producers, as proposed by De Loecker and Warzynski (2012). We explore systematic di erences across industries and plants. Our main ndings are that mark-ups are higher in capital-intensive industries, and for plants that are more productive, larger, and more capital-intensive. Our ndings are consistent with theories that predict larger mark-ups for more e cient rms and for higher quality products.Departamento de Economía