This paper presents an examination of regional concentration levels of individual industries in the Mexican manufacturing sector and its determinants. The shifts after NAFTA are particularly weighed up. We employ state level data of manufacturing output and employment (1988-2003). The data reveals that industries have become, on average, more dispersed in terms of both production and employment. However among the most concentrated industries are those which are highly linked to international markets. The concentrated, concentrating and largest industries tend to locate in traditional industrial regions, in the north but increasingly more in the Bajio. The regression analysis for the determinants of concentration shows consistency with a number of predictions such as the significance of economies of scale, wages, exports and transport costs, which indicates that international trade plays a role in concentration profiles of industries.