The work with almost extinct languages demands special strategies, and linguists are confronted with a number of limits in documenting and describing such languages. This paper presents two case studies of almost extinct Bolivian Tupi-Guarani languages, Jorá and Guarasu. The paper focuses on accounts of ethically difficult situations and discusses how the linguists have dealt with these challenges. It then shows our linguistic analysis of very limited datasets we have gathered and how with evidence from phonetics, morphology and lexicon, we can suggest an internal classification for these Tupi-Guarani languages.