The owl monkeys (Aotus sp.) are considered excellent experimental models for biomedical research, in particular for studies on vision 1 and malaria. 2 For such studies, the use of animals with normal liver function is crucial to ensure an adequate experimental protocol. The liver is involved in several physiological functions, including biosynthesis, detoxification, digestion, and immunity, being the major elimination pathway for several drugs. 3 Hepatic diseases may impair these functions and result in accumulation of toxins in the body, 4 which can affect experimental treatments. Monitoring hepatic function is therefore essential to avoid the impact of pre-existing liver conditions in the outcome of experiments.Liver conditions such as fatty liver disease, spontaneous gallstone formation, and focal nodular hyperplasia have been reported in Aotus trivirgatus, 5 Papio sp, 6 Saimiri sciureus, 7 Macaca fascicularis, 8