The mountainous and broken hill country in the middle part of the eastern shore of Lake Tanganyika is one of the areas which have been well studied primatologically. In particular, the chimpanzee has been studied for years by many primatologists at several sites. At least ten species of primates appear in this area. Nevertheless, the geographical range of some of these primates has been quite unknown. This paper proposes geographical maps and localities for these primates as well as brief ethological descriptions of them, a result of a survey throughout this area. Before the survey three species of primates in the area had been subspecifically unidentified. Two of them have proved to beCercopithecus ascanius schmidti andCercopithecus mitis doggetti, identified by Dr.W. C. Osman Hill, both of which are newly recorded in this area. The third is probablyColobus polykomos, but as no specimen or fur could be obtained, its taxonomic status remains obscure. In the last chapter of this paper, some zoogeographical problems concerning the primates of this area are discussed.