A cross-sectional parasitological study of a population of wild olive baboons (Papio cynocephalus anubis), consisting of 5 troops, was conducted in Gombe Stream National Park. Baboons were individually recognizable. Information on age, sex, troop membership, reproductive status, social rank and life-history of each individual baboon could be related to parasite infection. Seven helminth taxa and 2 protozoan taxa were found. All baboons were parasitized by at least 1 taxon. Distributions of helminths were aggregated among hosts. There were significant differences among troops in the prevalence of all but 2 of the recorded helminths. Age had a significant impact on the prevalence and intensity of Strongyloides sp. No significant effect of sex on the prevalence of infection could be detected. There was some indication that female reproductive status was related to Trichuris egg output. In contrast to a previous study, no significant correlations between parasite infection and social rank could be found. Troop membership constituted the predominant factor contributing to heterogeneity of prevalence of infection. This suggests that spatial location and/or genetics may be important in determining levels of parasite infection.