Three factors, environment, quality and type of interaction, and phylogeny have been hypothesized to influence the structure of signal repertoires in primates. Much is known about vocal repertoires of terrestrial, savannah-dwelling species and arboreal, rainforest-dwelling species, but very little is known about terrestrial rainforest species. To fill this knowledge gap and to further elucidate how the three factors influence vocal repertoires of primates, we designed a study on sooty mangabeys (Cercocebus torquatus atys), a terrestrial Old World primate that lives in dense rainforests. Recordings of sooty mangabeys in their natural environment were used to compile the vocal repertoire of this species. All calls are described according to the basic acoustical structure and the behavioral context in which they occurred. Descriptions are supplemented by quantitative measurements of call occurrence in all age–sex classes. For the most frequently produced vocalizations, a preliminary acoustical analysis was conducted to test for individual and contextual differences. Finally, we compare vocalizations of sooty mangabeys with vocalizations of several other primate species and discuss how the factors mentioned above might influence the vocal repertoire of sooty mangabeys.