Intertroop conflicts occur regularly in populations of chacma baboons (Papio ursinus) in a desert canyon in the Namib desert of South West Africa and in the Okavango Swamps of Botswana. These interactions range from peaceful mingling of juveniles to violent chases by adult males. Encounters may involve face-offs, coordinated group charges into the ranks of the opposing troop, intratroop herding by adult males, and vocalizations. Encounters between the desert canyon troops vary for the same troop, depending upon the alien troop encountered. In the desert, intertoop dominance was correlated with large troop size and the number of large males per troop. In the swamp, where neighboring troops shared more stable troop boundaries, intertroop interactions were more frequent and their character less variable. Adult females generally withdraw or are chased from encounter sites. When troops come together juveniles may initiate play or groom members of alien troops. Male baboons dominate intertroop encounters and are hostile in their interactions. Keywords: Namibia, Namib Desert, Kuiseb River, Botswana, Okavango Swamps, primate ecology, Papio ursinus, territorial claims, social mammals, animal behaviour, sociality.