this research is a collection of the numerous guarani lexicon and expressions found in hijo del hombre (son of man), a novel by the paraguayan writer augusto roa bastos. our purpose was to create a glossary. the term selection criterion was an expert reading, a native speaker of guarani. besides, two bilingual dictionaries were used to reinforce the study, one on paraguayanism and one on americanism. the procedures used by the author to achieve comprehension were the use of context, adaptation to the grammatical structure of spanish and the inclusion of guaranisms in colloquial phrases. a reading from the perspective of the translator and the lexicographer would not omit the study of the guarani expressions; this task uncovers an unsuspected richness on the part of the novelist handling his tongue filled not only with this type of lexicon, but also with paraguayanisms, purism and cultism that saturate the roabastian work.