(Uploaded by Plazi for the Bat Literature Project) The Atlantic Forest in the state of Espírito Santo, as in other regions, is a fragmented ecosystem and larger areas are protected in Conservation Units. The studies on the mammals in this region of Atlantic Forest have shown a high diversity, which makes it a highly relevant research. Herein we describe a survey of volant and non-volant mammal fauna in Duas Bocas Biological Reserve, carried out between January 1987 and December 1988. Live traps were used in order to capture non-volant small mammals. Medium- and large-sized mammals were recorded by direct and indirect observations. Bats were caught in day roost with hand nets and at night by standard mist nets. Seven orders, 17 families, and thirty-five non-volant species were recorded. Trinomys paratus (37.3%) and Didelphis aurita (24%) were the most captured species. Callithrix geoffroyi was much observed and may occur in population density of more than one individual per hectare. Among bats, two families and twelve species were recorded, with Carollia perspicillata and Artibeus lituratus captures being the most frequent, comprising 50% of the community surveyed. Caluromys philander, Leopardus guttulus, Puma concolor, Galictis cuja, Hydrochoerus hydrochaeris, Pecari tajacu, Sylvilagus brasiliensis, Mazama sp. and all bat species are new records for this forest reserve. Adding to the already recorded species, the Duas Bocas Biological Reserve comprises 59 mammalian species. Taking into account the species listed in this study, seven of medium- and largesized and a bat are on the Brazilian lists of endangered species.