This dissertation presents a comprehensive description of Xinka based on the missionary grammar Arte de la lengua szinca that was written by the priest Manuel Maldonado de Matos around 1773. Xinka is an isolate family of today mostly extinct, closely related languages in southeastern Guatemala. The Arte de la lengua szinca is the earliest source on Xinka grammar that is otherwise not well documented or described. The analysis of the late colonial grammar draws on comparative data, including (a) primary data that were documented by the author with the last Xinka-speakers in Guazacapán, Santa Rosa, Guatemala between 2000-03, and (b) further secondary linguistic data of Xinkan languages from the towns of Guazacapán, Chiquimulilla, Yupiltepeque, Jumaytepeque, Sinacantán and Jutiapa. The text addresses the methodological implications of describing colonial Xinka grammar based on such a heterogeneous corpus of diachronic and regionally diverse data. Besides the linguistic description, the dissertation contains information about the cultural context of the language as well as about the colonial document and the corpus of linguistic data. The appendix includes a concordance of the linguistic data from the colonial grammar and a dictionary of the lexical entries.