The cytogenetic studies of retrotranposons Rex have been characterized in several fish groups, including species of the Astyanax genus. This group presents an extensive variability in their karyotype, with diploid numbers of 2n = 52, 50, 48, 46 and 36 chromosomes. Thus, the aim of this study was to evaluate the distribution of the retrotransposable element Rex1, in six Astyanax species, with different diploid numbers. The species analyzed were Astyanax altiparanae (2n = 50), Astyanax asuncionensis (2n = 50), Astyanax eigenmanniorum (2n = 50), Astyanax marionae (2n = 48), Astyanax fasciatus (2n = 46) and Astyanax schubarti (2n = 36). Rex1 was dispersed in the Astyanax species, suggesting that these retrotransposons play important role in genome evolution.