IN 1929 LESLIE BYRD SIMPSON brought out his fine study The Encornenda in New Spain: Forced Native Labor in the Spanish Colonies,1 which represented pioneering and well-deservedly became a landmark in the study of the encomienda system. His 1950 revision and refinement of this work, The Encomienda in New Spain: the Beginning of Spanish Mexico,2 is so extensive that he has in many respects produced a new work in both organization and concept. This revision truly represents the progress of encomienda studies in the years which have elapsed between the appearance of the two volumes and will stand as one of the definitive works on the encomienda. As Simpson states, since his initial version appeared so much fundamental research on Spanish colonial institutions had been done, and knowledge and understanding of the encomienda had so expanded, that revision became essential. Simpson himself contributed much to this expanding knowledge of colonial institutions in connection with economic and demographic developments as well as directly in connection with the encomienda itself, thereby enrichening and maturing the content of his new volume.3 His approach in this revision consequently represents new demographic and economic lines of attack in the study of the encomienda. An advance of this type has been made possible through continuing research by the company of