An animal's behavior is related to its parasitological fauna. More proactive and sociable individuals risk being in contact with parasites; once infected and energetically compromised, they modify their behavior. This modification depends on individual differences on the host (ex.: sex, age, hierarchical position) and parasite characteristics (ex.: life cycle, transmission mode). This project analyses possible relationships between personality axes, blood parameters, environmental parameters, and gastrointestinal parasite load in capuchin monkeys kept in different conditions: captive Sapajus spp. (CETAS RN; PB) and semi-free-living blond capuchins (Sapajus flavius) in Atlantic forest fragment. We hypothesize that: a) adult males, b) with higher proactivity, and c) with higher social network centrality will show higher parasite load and lower number of immune cells. For semi-free-living capuchin monkeys, we hypothesize that: a) adult males, b) during dry season will show higher parasite load. Therefore, blood samples will be collected during routine veterinarian exam on CETAS, and fecal samples will be collected opportunistically in both environments for parasite detection and counting. Using questionnaire and behavior observation, we will define personality axis and build social networks. We will test our hypotheses by multivariable model selection through Akaike Information Criteria. We intend the results to be useful for applied management of captive capuchins, identification of parasites in semi-free-living capuchin monkeys for possible zoonosis control, and theorical use of capuchin monkeys as translational models for the evolution of the relationship between personality, group life and parasitism.