The objective diagnosis of thoracic outlet syndrome (TOS) remains a challenge. The purpose was to present our experience and discuss the utility of electromyography, electroneurography and somatosensory evoked potentials after ulnar nerve stimulation in patients with surgically verified neurovascular compression at the thoracic outlet. Twenty patients (median age 29.5, 16 women) with operatively verified neurovascular compression by a cervical rib or band were examined. All complained of pain and paraesthesias in the hand. In 12 vasomotor disturbances (pallor or lividity, low skin temperature, Raynaud's phenomenon) were also observed. Clinical diagnosis was supported by the provocative tests (Adson, Wright, costoclavicular) in 14persons. Neurologic signs were present in 2 patients in "pseudoulnar" distribution. Anterior scalenectomy was performed with success in 15 cases, 4 remained unchanged and 1 worsened. Electrodiagnostic tests were normal in all 18 patients without neurologic signs. We note a tendency for the digital nerves sensory action potentials in patients with TOS to be higher than usual It is concluded that electrodiagnosis is useless in confirming the presence of TOS, but it is very useful to exclude other painful conditions that require other treatments (carpal and cubital tunnel syndromes, cervical radiculopathies etc).