To investigate the involvement of the visceral afferent nerves in diabetes mellitus, we enrolled 46 male patients in a study, examining the cerebral potentials evoked by stimulation of the vesico-urethral junction (VUJ CEP) and the pudendal (penile CEP) and posterior tibial nerves (tibial CEP). The age range was 23-67 (mean 45.8) years. The epithelial surface of the vesico-urethral junction was stimulated bipolarly with an electrode attached to a specially produced Foley catheter. Cerebral responses were recorded bipolarly at vertex. VUJ CEPs were absent (27 patients) or protracted and/or of low amplitude (4 patients) (total 31 patients; 67.8%). Penile CEP and/or tibial CEP could be obtained in all cases; however, protracted P1 peak latencies were detected in 15 (32.8%). The abnormalities of VUJ CEP did not correlate with the presence of peripheral neuropathy, while the abnormalities of penile CEP and/or tibial CEP invariably coincided with the presence of peripheral neuropathy. Although neither age nor the duration of diabetes correlated with abnormal CEPs as determined by any of the tests, insulin dependence correlated with abnormal penile CEP and to a lesser extent with VUJ CEP. We conclude that VUJ CEP is informative in evaluating the physiological condition of visceral afferents, and can be used in diagnosis of the early involvement of visceral afferents in diabetes mellitus.