PURPOSE: Although communications between branches and cords of the brachial plexus have been extensively published, there is a scarcity of reports concerning radial and ulnar nerve (RN-UN) communication in the arm. The current study aims to demonstrate the incidence, topography, and length of communicating branches between RN and UN. Any additional coexisted variations were also recorded.MATERIALS AND METHODS: Two hundred and sixty-six upper limbs collected from one hundred and thirty-three (81 males and 52 females) Greek cadavers were dissected.RESULTS: Three out of one hundred and thirty-three cadavers, accounting for an incidence of up to 2.3%, were found to have an atypical communicating branch originating at a high humeral level from RN towards UN. In two cadavers, communicating branches were detected on the left side and in one cadaver bilaterally.CONCLUSIONS: The study of atypical communications between RN and UN attracts great attention for its clinical importance, mainly in cases of peripheral neuropathies with diagnostic dilemma or upper limb nerve injury producing an otherwise unexpected symptomatology due to the aberrant nerve supply. Familiarity with these variations is crucial in avoiding misdiagnosis and preserving valuable communicating branches, thus achieving an uneventful outcome in cases of upper limb nerve injury repair.