RESUMEN
BACKGROUND: Callithrix jacchus is a small primate widely used in experimentation, but data on plasma total protein (PTP) values of free-living animals inhabiting its own endemism region are non-existent. METHODS: Marmosets belonging to two free-living groups were captured for marking and obtaining biological material. The collected blood was centrifuged to obtain the plasma and thus to determine the concentration of PTP. RESULTS AND CONCLUSIONS: Females and adults had the highest mean PTP. Mean found were higher than other values described for other neotropical primates, and the high PTP values presented by the animals indicate dehydration. Due to the importance of total plasma proteins for health and management, obtaining these values as a reference is relevant for the free-living Callithrix genus and other neotropical primates.