The Holy Office of the Inquisition in colonial Mexico had as its purpose the defense of Spanish religion and Spanish-Catholic culture against individuals who held heretical views and people who showed lack of respect for religious principles. Inquisition trials of Indians suggest that a prime concern of the Mexican Church in the sixteenth century was recurrent idolatry and religious syncretism. During the remainder of the colonial period and until 1818, the Holy Office of the Inquisition continued to investigate Indian transgressions against orthodoxy, and to provide the modern researcher with unique documentation for the study of mixture of religious beliefs. The “Procesos de Indios” and other subsidiary documentation from Inquisition archives present crucial data for the ethnologist and ethnohistorian, preserving for him a view of native religion at the time of Spanish contact, eyewitness accounts of post-conquest idolatry and sacrifice, burial rites, native dances and ceremonies as well as data on genealogy, social organization, political intrigues, and cultural dislocation as the Iberian and Mesoamerican civilizations collided. As “culture shock” continued to reverberate across the seventeenth and eighteenth centuries, Inquisition manuscripts reveal the extent of Indian resistance or accommodation to Spanish Catholic culture.