Potential resource overlap between howling monkeys and other arboreal mammals was studied in the rain forest of Los Tuxtlas, Veracruz, Mexico. Eight species of mammals belonging to the orders Primates, Carnivora, Rodentia, and Marsupialia were found to share the canopy and to overlap trophically with howling monkeys. These mammals made up 77% and Alouatta 23% of the arboreal mammalian biomass under consideration. The arboreal porcupine and spider monkey were the only mammals that also fed on leaves. However, in this feeding niche, Alouatta is the only important mammalian folivore in Los Tuxtlas, and resource depression derived from leaf-eating insects is more important. The eight arboreal mammals may exert more pressure upon fruit resources, for they consumed 75% of the estimated total dry weight of fruit/ha/yr consumed by arboreal mammals.