During reorganisation of the paleontology collections at the Department of Antiquities and Museums, Kampala by the Uganda Palaeontology Expedition, several primate postcranial remains from Napak, an Early Miocene site, were found. Several large limb bones are attributed to Proconsul major, already known from the locality on the basis of dental and gnathic remains, but hitherto poorly known postcranially. One specimen belongs to a smaller species of hominoid not represented at Napak by teeth and jaws. Both hominoids show quadrupedal and climbing adaptations, but they differ from each other. Thus Proconsul major praticed 'power' climbing whereas the smaller hominoid would have been more 'agile'. In both cases, the hominoids moved frequently between the trees and the ground, and both were well adapted to their palaeoenvironment, which was dry forest. A further important result of this study is that the postcranial remains of P. major indicate that it was heavier than had previously been envisaged on the basis of its dental remains. It would have weighed about the same as female gorillas, between 75 and 90 kg. The small species weighed about 20 kg.Lors d'un reamenagement des anciennes collections paleontologiques de l'Uganda Museum, des restes postcraniens de primate provenant du site Miocene de Napak ont ete retrouves. Certaines pieces de grandes dimensions sont attribuees a Pronconsul major, deja signale sur le site a partir de restes dentaires et gnathiques, mais dont l'anatomie postcranienne etait mal connue. D'autres specimens sont rapportes a un Hominoidea de plus petite taille et non represente par des dents ou des machoires. Les deux hominoides montrent des caracteristiques de quadrupedes pratiquant le grimper mais de facons differentes. Alors que Pronconsul major pratique un grimper puissant, l'Hominoidea de petite taille pratique un grimper plus agile. Quoi qu'il en soit, ces deux especes se deplacaient souvent et activement au sol et dans les arbres. Ils vivaient dans une foret seche. Cette etude confirme que Proconsul major, Hominoidea de grande taille, avait une masse corporelle plus importante que celle envisagee auparavant a partir des mesures dentaires. Il devait avoir une masse equivalente a celle d'un gorille femelle et peser entre 75 et 90 kg. L'espece plus petite, quant a elle, aurait pese 20 a 25 kg environ.