Mayan civilization, renowned for its mathematics, writing, architecture, religion, calendrics, and agriculture, fascinates scholars and a wide lay public as archaeology and glyphic decipherment reveal more of its secrets. In this pathfinding study of the Mayan language family, John S. Robertson explores major changes that have occurred in the core of Mayan grammar from the earliest, reconstructed ancestral language down through the colonial languages to the modern languages that are spoken today. Building on groundwork already laid in phonological studies and in the study of the pronominal system, Robertson's examination of tense/ aspect/ mood/voice is the next logical step in the general linguistic study of Mayan. Robertson offers careful consideration of all the major subgroups of Mayan, from Yucatecan to Quichean, as they are spoken today. He also draws extensively on colonial documents assembled by bilingual Spanish-Mayan speaking clerics. These documents provide a check on the accuracy of both the reconstructed ancient language, Common Mayan, and the theoretical evolution of the modern languages from this ancestor. The study will also be of value to students of the Maya glyphs, since it discusses the grammatical system that most probably underlies the glyphic representations. Beyond its obvious interest for Mayan linguistics, the study proposes a theory of language change that will be important for all students of comparative linguistics. Robertson's work sets forth the basic, universal assumptions that provide for an appropriate description of the grammatical systems of all languages. It will be a significant reference for future researchers.