The internal classification of Mixtec is controversial. Many varieties are mutually unintelligible and by that criterion separate languages. In the 16th century, Spanish authorities recognized half a dozen lenguas comprising the Mixtec lengua. (See #Classical Mixtec.) It is not clear to what extent these were distinct languages at the time. Regardless, the colonial disintegration of the Mixtec nation and resulting isolation of local communities led to the rapid diversification of local dialects into distinct languages. Below are some attempts at Mixtec classification by various scholars.
Josserand (1983:106) lists 5 major geographic (not linguistic) divisions of Mixtec, which together cover a total of about 25,000 square kilometers. Enclaves of Amuzgo, Trique, Cuicatec, Ixcatec, and Chocho speakers are scattered nearby.
De los Reyes, in his Arte de Lengua Mixteca (1593), spoke of half a dozen lenguas in the Mixtec lengua. To these, his contemporaries added the dialects of Guerrero:
Josserand found that native mundane writing of the colonial era corresponded well to de los Reyes; based on phonological and orthographic consistencies, she divides the dialects into five groups, as follows:
The following classification is given by William R. Holland (1959), as cited in Josserand (1983:134-135). This preliminary classification is a glottochronological study of the dialects of 22 Mixtec and 4 Cuicatec towns.
Holland (1959) also gives 3 areal groupings for these zones.
However, Josserand (1983) states that these groupings are based on flawed methodologies, including a faulty conception of the geographical layout of the Mixteca. Many towns that Holland listed as Baja are in fact Alta, and vice versa.
The following classification is given by Evangelina Arana-Osnaya (1960:257), as cited in Josserand (1983:137).
Cornelia Mak and Robert Longacre (1960) is the first reconstruction of Proto-Mixtec, which is the ancestor of Mixtec proper as opposed to Mixtecan. Below is a classification inferred from Mak & Longacre (1960) by Josserand (1983:142). 9 groups and a total of 28 towns are given.
The following classification is given by Richard Spores in The Mixtec Kings and Their People (1967), as cited in Josserand (1983:128). A total of 18 dialects are given.
The following classification is given by C. Henry Bradley (1970), as cited in Josserand (1983:132). A total of 11 dialects are given. His classification was most likely based on SIL International's mutual intelligibility surveys.