The objective of the study was to present electrodiagnostic and clinical findings of the traumatic disease of brachial plexus (TDBP). Dogs and cats that had clinical signs of TDBP and diagnosed electrophysiologically were reviewed. Standard motor nerve conduction study and/or sensory nerve conduction studies, H reflex, somatosensoric evoked potentials, and needle electromyography in both extremity and paraspinal muscles were employed for diagnosing the involved nerve and level of injury. Injured areas were examined in three cases (1 dog, two cats) after euthanasia and in 10 cases (4 dogs, 6 cats) during operation at the lower part of brachial plexus by the reflexion of the scapula laterally. The left side was predominant in both dogs and cats in 81.82 % and 76.47% respectively. The radial nerve was involved in all cases individually or associated with other nerves. There were avulsion in radial nerve (n=11) and at the outside of vertebral canal or lower spinal ganglion (n=4), and the other cases had multiple nerve involvement in brachial plexus as in ulnar-median, axial, musculocutaneous and suprascapular nerve in addition to radial nerve. The injured nerves were found totally severed and lodged in fibrous tissues ventrally at the operation or necropsy. However in two surgically explored cats epineurium remained partially intact. In conclusion, sensory nerve action potentials, and needle EMG and H reflex can be suggested in determining the avulsion of the brachial plexus, denervation potentials can be accepted as a clue to diagnose the involved nerve.