The karyotypes of three monkeys from the genus Aotus were studied by using banding techniques, including G, C and Q bands. The blood samples for cellular culture were taken from individuals kept in captivity at the Centro de Rehabilitacion de Fauna Silvestre del Oriente de Caldas (CRFSOC), La Victoria (Caldas) where the animals were being kept temporarily after being confiscated from illegal species traffickers. The blood samples were processed at the Universidad Nacional de Colombia's Cytogenetics Laboratory in Bogota. Two karyological configurations were found: 2n=52 XX; NF=72, 20 Bi, 32 A. and 2n=53 XX; NF=72, 20+1XX Bi, 30 A. The last one presented a simple robertsonian centric-fusion of chromosomes 13 and 14. The chromosomes were classified into three groups according to size and morphology: A metacentric, B submetacentric, and C acrocentric. It was concluded that the cytogenetically analyzed individuals belonged to the gray necked group identified as Aotus griseimembra, a species distributed throughout certain areas in the middle Magdalena river valley, Colombia.