Long term use Dyphenylhydantoin (DPH) was shown to induce sensory-motor peripheral neuropathy. However, we found no report on DPH induced impairment of autonomic nerve function. On the other hand, during DPH therapy patients often complain of loss of libido and sexual impotence, and patients sexual dysfunction could be related to peripheral autonomic neuropathy. Sympathetic skin response (SSR) is a useful method for assessing autonomic sympathetic nerve dysfunction, In this study, we compared sympathetic skin responses, evoked by deep inspirium, in 30 male epileptics on DPH therapy with those in 30 age matched healthy controls, SSRs were obtained in all the patients suggesting that DPH does not induce sympathetic autonomic neuropathy. However, patients were found to have significantly longer latiencies. Hyperpolarising effect of DPH on neural structures may be responsible for delayed latencies