The Lama forest is the largest natural forest in southern Benin, and one of the last remnant forests within the Dahomey Gap. It harbours several species of major importance in terms of conservation. Small mammals are known to represent more than 80% of the African mammalian species diversity but they have received little attention in Benin. In this article we present the results of the first terrestrial small mammal species inventory (murid rodents and shrews) in the Lama forest. In September and October 2007, we captured 280 small mammals belonging to 12 species, identified by morphological and genetic analysis. We also provide detailed cytogenetic data for six of the 12 captured species. For five of them, we compare our data with previously published karyotypes, and for the sixth one (Hylomyscus pamfi), the karyotype is published here for the first time. Two of the captured species are closed-forest specialists (Praomys misonnei, H. pamfi), and H. pamfi is endemic to the Dahomey Gap region. Our results are congruent with those obtained on other animal groups, and highlight the importance of the Lama forest for the conservation of the country's forest biodiversity.