flexor digitorum profundus muscles in the Saguinus leucopus. Methodology: Both thoracic limbs of ten specimens were dissected from superficial to deep; describing the shape, origin, insertion, innervation and arterial supply for these muscles. Main results: The flexor digitorum superficialis muscle originated in the medial epicondyle of the humerus and sent tendons for the digits II-V; and the flexor digitorum profundus muscle had a high development with six heads: two humerals (superficial and deep), one radial, one cubital, and two ulnar (superficial and deep), which form a single tendon that divides distally to the carpus in five tendons to go to each digit. Conclusion: These muscles in Saguinus leucopus are adapted to allow for an adequate grip onto the branches and trunks of the trees, and to release the cortex for the flow of the latex.