Despite all the pressures for changing the ways of American Indians into those of the white man, there are still basically Indian systems of social structure and culture persisting with variable vigor within conservative nuclei of Indian population. The author outlines a conceptual framework for the analysis of American Indian acculturation in different areas of the United States, provides a brief synoptic review of the degree of acculturation in such areas, and discusses the limiting factors to full acculturation by comparing the situation of the United States with that of Mexico, and considers the development of "Pan- Indianism" as an emerging stage in the acculturation process.—Ed.