A preliminary survey targeting flies associated with wild chimpanzees was carried out at the Mahale Mountains National Park, Western Tanzania, during the November-December rainy season of 1995 and 1996. A total of 16 genera and 35 species belonging to 5 families (Tabanidae, Glossinidae, Muscidae, Sarcophagidae and Calliphoridae) were collected. Of these, 5 genera and 10 species of 3 families, namely Haematopota nigripennis, H. unicolor, H. theobaldi, Haematobosca wooffi, Stomoxys transvittatus, S. pallidus, S. omega, Sarcophaga (Xanthopterisca) elegantipes, Neomyia limbata and N. difficilis were new records for Tanzania. The fly fauna was characteristic of central Africa, rather than East Africa. Two tsetse fly species, namely, Glossina morsitans morsitans and G. longipennis, were collected in the vicinity of chimpanzee populations. Although G. longipennis rarely feeds on primates, many blood meals from this species were experimentally confirmed to be of primates origin. Sarcophaga (Bercaea) aruno was the main species attracted to chimpanzee excrements.