This study provides descriptive data pertaining retroflex consonants /ɻ/ and /ʈ͡ʂ/ from Mapudungun spoken in Alto Biobío, for the purpose of determining their allophonic variants, their frequency and, by doing so, to also compare these observations with those of previous studies. The data comes from 10 adult speakers (5 female and 5 male). Results showed that /ɻ/ displays 3 allophonic realizations: [ɻ], [ɻγ] and [ʐ], and two in the case of /ʈ͡ʂ/: [ʈ͡ʂ] and [t]. The comparison of these phonetic variants and their frequencies of occurrence with those of other varieties within eastern Mapudungun highlights the fact that in Alto Biobío a velarized approximant [ɻγ] and a retroflex plosive [t]—both, very uncommon in other dialects—occur with frequencies of 11 % and 30 %, respectively.