Rémi Siméon is best known for his Náhuatl-French dictionary (1855) and his edition of Chimalpahin (1889). This brief treatise on Náhuatl grammar was prepared as an introduction to the dictionary and has already been published twice in Spanish in the 20th century, once by Cicilio A. Robelo (1902) and again in the most recent volume of Estudios de cultura náhuatl (1962). Less comprehensive than the Llave of Garibay, and more scientific than the 16th century Artes of Molina and Olmos, it is a lucid statement of syntax and word formation. The presentation is conservative, didactic, and uncomplicated. Siméon regarded Náhuatl as a sonorous but simple tongue, reducible to a small number of linguistic principles. His work treats essentials in a straightforward way and, for the most part, avoids grammatical exceptions and refinements. Phonetics, nouns, adjectives, numbers, pronouns, verts, suffixes, and adverbs are taken up in order, with some examples and paradigms but without the textual excerpts that so enrich Garibay’s Llave. The latter remains the most useful of the Náhuatl treatises for the modern student.