Western Mexico is vast and geographically diverse and has received far less attention compared to other areas of Mesoamerica. Research over the past decade allows the definition of four major subregions characterized by cultural factors and distinct historical trajectories. A large proportion of the research in western Mexico is still culture-historical in nature, oriented toward establishing chronologies and relationships between regions. But along with a number of recent efforts toward synthesis and consolidation, current theoretical research contributes to the study of mortuary patterns and social organization, alternative forms of social complexity, agricultural intensification, empire formation, state involvement in the economy, human-land relationships, and the interlocking relationship between migration and sociopolitical reorganization.