ABSTRACT. Duarte R., dos Santos-Clapp M.D. & Brasil-Sato M. de C. [Endohelminthes of Salminus hilarii Valenciennes (Actinopterygii: Bryconidae) and their ecological descriptors in the upper São Francisco River, Brazil.] Endohelmintos de Salminus hilarii Valenciennes (Actinopterygii, Bryconidae) e seus índices parasitários no rio São Francisco, Brasil. Revista Brasileira de Medicina Veterinária, 38(supl. 3):194-205, 2016. Programa de Pós-Graduação em Ciências Veterinárias, Anexo 1, Instituto de Veterinária, Universidade Federal Rural do Rio de Janeiro, BR 465, Km. 7, Campus Seropédica, RJ, Brasil, 23897-970. E-mail: email@example.com Among the fish encountered in the upper São Francisco river, Salminus hilarii, popularly in portuguese known as "dourado-branco" is a migratory briconid fish. A top carnivore in the food chain, that presents high commercial value and interest in fish farming and sport fishing. In this work, the endoparasites species of S. hilarii parasitic fauna were identified based on thirty-three specimens of fish from Três Marias reservoir, (18º12’51’’S 45º15’51’’W), State of Minas Gerais. Larval Eucestoda specimens (plerocercoids of Proteocephalidea), larval and adults/juveniles specimens of Nematoda were found. Amid of these nematodes, Hysterothylacium sp. was present in all the fish analyzed (Prevalence, P=100%) followed by Contracaecum sp. (P=60.6%), Spiroxys sp. (P=48.5%) and Goezia sp.1 (P=45.5%). The higher prevalence of Anisakidae larvae, mainly of Contracaecum sp., in relation to the other families is relevant. This study evidenced the importance of S. hilarii as an intermediate and paratenic host due to the great variety of Eucestoda and Nematoda larvae found; the adults and juveniles specimens from three important nematode families found in S. hilarii emphasize their paper as a potential definitive host due to their activities as a predatory fish in the reservoir. Salminus hilarii, from the upper São Francisco river, constitutes a new host for endoparasites species, Hysterothylacium sp., Contracaecum sp., Goezia spp., Spiroxys sp. and Rhabdochona acuminata, found in this work.