Collado's work, derived in all its significant features from the _Arte da lingoa de Iapam_ completed in 1608 by João Rodriguez, is in a strict, scholarly sense less valuable than its precursor. However, if used with the _Arte_ as a simplified restatement of the basic structure of the language, Collado's Grammar offers to the student of the Japanese language an invaluable ancillary tool for the study of the colloquial language of the early 17th Century. While less extensive and less carefully edited than the _Arte_, Collado's Grammar has much to recommend it as a document in the history of grammatical description. It is an orthodox description attempting to fit simple Japanese sentences into the framework established for Latin by the great Spanish humanist Antonio Lebrija. Thus, as an application of pre-Cartecian grammatical theory to the structure of a non-Indo-European language, the _Ars Grammaticae_ is an important document worthy of careful examination by those wishing insight into the origins of what three centuries later was to become the purview of descriptive linguistics. The present translation was begun with the able assistance of Ms. Roberta Galli whose contribution to my understanding of the Latin text is most gratefully acknowledged. For his continued encouragement in this undertaking I am grateful to Professor Roy Andrew Miller. Thanks are also due to the Graduate School of the University of Kansas for its support in the preparation of the manuscript and to Ms. Sue Schumock whose capable typing turned a scribbled, multi-lingual draft into a legible manuscript. The imperfections are my own. R.L.S. Lawrence, Kansas May, 1975 {1} * * * * * Introduction In 1632, as the Christian Century in Japan was drawing swiftly to a close, three works pertaining to the Japanese language were being published at Rome by the Congregation for the Propagation of the Faith. These works were by the Spanish Dominican Father, Diego Collado (d. 1638), who had spent the years from 1619 to 1622 in Japan. Their publication clearly reflects the vitality of the missionary spirit in that age as well as the important place reserved for language study in the propagation of the faith.