1. The galvanic skin response (GSR) elicited by pin prick and light touch was tested in seven patients with organic (traumatic) interruption of the peripheral sensory pathway; in one patient with complete (traumatic) transsection of the spinal cord and in seven patients with hysterical anesthesias.2. A new method, of recording the GSR with the Grass electroencephalograph, as suggested by Luther Mays, is described and used.3. In patients with organic anesthesias due to complete peripheral nerve and complete cord lesions no GSR could be obtained on stimulation of the anesthetic zone by pin prick and light touch.4. In all hysterical patients the GSR elicited by stimulation of the anesthetic zone by pin prick and light touch was normal.5. Thus the described test offers an objective method of differential diagnosis between organic and functional anesthesias.6. The results of this investigation support the thesis that functional anesthesia is a result of inattention to the sensory input from the anesthetic area. Such inattention (or dissociation) may be, in rare and extreme cases, of a conscious nature as in malingering; or due to various degrees of repression from the conscious as in hysterical reactions. However, sympathetic responses in malingering and hysterical reactions do not differ.