The paper describes social and economic differences between Monterrey's eight municipalities, including housing conditions and basic service provision, and how these changed between 1970 and 1990. It also describes the social and economic differences for 1990 between the 710 micro-areas into which Monterrey was divided which allows a more precise and detailed picture of intra-urban inequalities. It also reveals the limitations of an intra-urban analysis based on municipal boundaries by showing many clusters of micro-areas with very low levels of socio-economic development in some of the better off municipalities.