For several decades, the phenomenon of irregularity in urban land tenure has been central element in the growth of Latin American cities. In the case of Tijuana, informal settlements have proliferated through the city’s history as a result of spectacular population growth, a significant share of the population’s lack of economic capacity to acquire housing, a limited supply of land in the real estate market for housing construction, local topographical obstacles, and institutional weaknesses in all three levels of government that prevent the orderly oversight of property rights and urban development. According to the findings of this study, more than half of currently occupied dwelling units in the Tijuana had irregular origins. In the context, the book embodies a systematic approach to the study of land tenure informality in the city. The research findings address the location and dimensions of informal settlements; their implications for housing quality and availability of basic public services and urban infrastructure, as well as implications for local real estate markets; and the limitations of the public institutions charged with housing production and supervision and with the process of land tenure regularization. The research presented here retains its currency and topicality ten years after it was carried out. This English edition is an effort to contribute to debate and analysis about one of the central issues in economic and social progress in every large city in the developing world.