Red Lists are important conservation tools because they attempt to estimate the extinction risks of species. We compared the conservation status of Brazilian mammals presented in the Brazilian Red Book with those presented in the IUCN Red List, highlighting the importance of each list and why they should be used jointly. Out of 636 species, 181 were considered endemic to Brazil and 121 were considered threatened by at least one of the lists. Considering the complete database, 86 % of the species had the same status on both lists, whereas only 48 % of the threatened species had the same status. Some possible factors responsible for variations are the period in which the evaluations were carried out, the evaluation process and the fact that a species threatened nationally may not be threatened globally. We recommend that communication should be improved, that lists should be kept updated, and that both the type of information and the data itself to be used in the assessments should be standardized.