The study of proximal motor and sensory nerve conduction in the thoracic outlet syndrome is still difficult and laborious in 1994. However, these conductions can be measured at different levels by means of somaesthetic evoked potentials and motor evoked potentials, when one takes the time to perform them. The study in normal subjects demonstrates that the proximal sensory and motor conduction delays are approximately 3.2 ms and are therefore comparable to that of the median nerve at the wrist. The study of 7 cases related to various diseases shows that these techniques, performed after electromyogram of both upper limbs, an essential prerequisite to their interpretation, are able to clearly demonstrate abnormalities of proximal conduction in patients suffering from of a scalene syndrome, a cervical epiduritis, radiation plexopathy, hereditary sensible to pressure neuropathy, motor neuropathy with persistent multifocal conduction blocks, or, on the contrary, may confirm the normality of conduction, for example in anterior horn disease.