Author Institution: Division of Biological Sciences, University of Michigan, Ann Arbor, and New York Zoological SocietyExperimental walks with a tame primate reveal that free living primates are likely to be subject to frequent infestation by ticks. Observations on the grooming behavior of mangabeys, red colobus and blue monkeys demonstrated that self grooming is primarily directed to parts of the body not subjected to allo-grooming, and that its role is a cursory brushing away of loose particles rather than a detailed cleansing. Allo-grooming is directed towards the detailed cleansing of the skin and fur, and is associated with frequent particle removal. Length of body fur has a considerable influence on the amount of grooming different parts of the body receive. I suggest that sexual dimorphism, age, sex and dominance status are important in determining rates of ectoparasite acquisition, and so the amount of grooming individuals need and receive