As of 2008, the Mexican government recognizes thirty varieties that are spoken in Mexico as languages (see the list below).

Little work has been done in the way of the historical linguistics of Nahuatl proper or the Aztecan (nowadays often renamed Nahuan) branch of Uto-Aztecan.

This binary division of Aztecan (Nahuan) was already the majority opinion among specialists, but Campbell and Langacker's new arguments were received as being compelling.

She shows the historical basis for the five verb classes, based on how they form the perfect tense-aspect, and she shows that all of the different forms of the perfect tense-aspect derives from a single -ki morpheme that has developed differently depending on the phonological shape of the verb to which it was suffixed.

Benjamin Lee Whorf (1937) had performed an analysis and concluded that /t͡ɬ/ was the reflex of Proto-Uto-Aztecan */t/ before /a/ (a conclusion which has been borne out).

As a geographical note: the northern part of the State of Puebla is universally recognized as having two subgroupings.

Canger (1978; 1980) and Lastra de Suarez (1986) have made classification schemes based on data and methodology which each investigator has well documented.

Canger recognized the possibility that centuries of population migrations and other grammatical feature diffusions may have combined to obscure the genetic relationships (the branching evolution) among the dialects of Nahuatl.

Some of the isoglosses used by Canger to establish the Peripheral vs. Central dialectal dichotomy are these: Lastra de Suárez in her Nahuatl dialect atlas (1986) affirmed the concept of the Center/Periphery geographic dichotomy, but amended Canger's assignment of some subgroupings to the Center or the Periphery.

The dialectal situation is very complex and most categorizations, including the one presented above, are, in the nature of things, controversial.

As a result, one can give greater or lesser importance to a feature and make the [dialectal] division that one judges appropriate/convenient" (1986:189).

A. Hasler sums up the difficulty of classifying Zongolica thus (1996:164): "Juan Hasler (1958:338) interprets the presence in the region of [a mix of] eastern dialect features and central dialect features as an indication of a substratum of eastern Nahuatl and a superstratum of central Nahuatl.

The extinct Classical Nahuatl, the enormously influential language spoken by the people of Tenochtitlan, the Aztec capital, is one of the Central dialects.

Lastra in her dialect atlas proposed three Peripheral groupings: eastern, western, and Huasteca.

Lastra's classification of dialects of modern Nahuatl is as follows (many of the labels refer to Mexican states): This list is taken from the Instituto Nacional de Lenguas Indígenas (INALI)'s Catálogo de Lenguas Indígenas Nacionales.