These aim of this study was to determine the richness and diversity of species in a low-hill forest of the forestry concession for timber purposes of the company Aserradero Forestal Becerra EIRL, Mazan, Loreto. 46 sampling units of 10 m x 500 m were evaluated. A total of 2418 trees are reported, grouped into 90 species, 76 genera and 28 botanical families. Virola sp. with 559 trees (23,12%) is the species with the highest number of trees, followed by Eschweilera albiflora with 559 trees (11,50%). The curve obtained from the diametric distribution of the number of trees looks like an “inverted J”, which indicates a higher number of individuals in the lowest classes and, as the diameter increases, the number of individuals gradually decreases. The most important species are Virola sp. (48,76%), Eschweilera albiflora (25,34%), Licania triandra (15,07%), Perebea guianensis (14,12%), Ocot...