||This dissertation is a grammatical description of several features of the morphology and phonology of the Mocho' language. Mocho' (Motozintleco) is a Mayan language spoken in the Chiapas region of Mexico near the border of Guatemala. It is moribund, with fewer than 30 remaining speakers, all over the age of 70 and bilingual in Spanish. Mocho' is a language with several features of interest, but which has not yet been the subject of a full linguistic description. This dissertation, based on data collected during several field trips and supplemented with unpublished data from previous researchers, provides an overview of the grammatical structure of Mocho'. The topics covered include phonology, loanwords, root structure, derivation and inflection of the different word classes, and important discourse particles. Mocho' is of special interest in Mayan linguistics as well as linguistic theory in general for many reasons. For example, Mocho' is one of only four Mayan languages to develop a tonal contrast; the Mocho' pattern is unique and has developed recently. Mocho' has several grammatical features which are unique in Mayan, including the development of middle voice from Proto-Mayan antipassive marking and the patterning of positionals, negatives, and syntactic markers of direction, location, and motion. Mocho' has a split ergative system, with ergative marking on third persons and nominative-accusative marking on first and second persons. Mocho' also has unique patterns of definiteness and evidentiality. This dissertation provides a description of Mocho' morphological and phonological structure in several areas, including those described above.