Henri Henrikhovitch Manizer (1889–1917) was a Russian ethnographer and linguist who spent six months among the Botocudo people from the Southeastern region of Brazil in the beginning of the twentieth century. His research was the result of a Russian expedition through South America in 1915. Manizer was the first researcher who was able to write down the Botocudo language with the most developed method of his time: the International Phonetic Alphabet transcription (Sebestyén 1981). Although many ethnographers had visited the Botocudo people before him, the material he collected is in many aspects of great value but it still remains unexplored both by linguists. This material includes bilingual Botocudo-Portuguese tales: a bilingual dictionary, articles and notes on the Botocudo grammar and culture, and a description of his impressions of the group. In spite of the good quality of the data, still many problems can be reported, such as the variations registered in the language transcriptions, the difficulties in transcribing some phonetic sounds (like voiceless nasals and contour segments, for example), the translation into Portuguese, problems with comprehension of the morphological and syntactic aspects, and cultural barriers (Seki 1984, 1985, 2001, 2004). In this paper, we aim to show our current research on this matter and present some of the partial results of this investigation based on the linguistic data by Manizer. We found out that our synchronical study of the phonology of the Krenak language, the only language of the Botocudo group which is still alive, leads to a better understanding of this old material, although there will remain still some unanswered questions. It enables us to formulate some hypotheses on what may have happened to the language and, maybe, to predict and understand its changes through time. As a result, we shall be able to work with this old material and make it available for both scholars and speakers of the language.