The alphabetization of the Nahuatl language represents the first European experiment in the transformation of an American language into a literary language, an experiment realized in a fashion parallel to the first studies of the European vernaculars. This alphabetization was realized in a long process from the earliest contacts to the middle of the 17th century. It is possible to discern at least three stages. The first corresponds to the period which immediately folows the conquest (1523–1547). All efforts were concentrated at the time on the learning of the language, a learning without precedent, resulting in its being cast in the Procrustian bed of the orthographic conventions of Castillian. The goal was not proper alphabetization. The second stage (1547–1595) corresponds to a period in the deepening of the knowledge of Nahuatl, a process reflected in the first ‘artes’ or treatises and vocabularies. This improved knowledge of the language led to the realization that a more appropriate orthography was required. The third and final stage in the alphabetization of Nahuatl (1595–1673) is characterized by linguistic research which no doubt has its antecedents in the investigation of other ‘exotic’ languages and which is aimed at an improved analysis of this language of Mexico. The orthographic endeavours are now directed toward a reform of the writing system which includes the introduction of new characters in an attempt to capture the phonological particularities of Nahuatl. From this history of the long process of alphabetization, it is evident that a detailed analysis of the phonological descriptions and the orthographic principles conserved in the treatises until 1673 not only allows us to appreciate the achievements of these early linguists but also provides us with valuable information about the phonological system of classical Nahuatl as well as of Castillian of the period.