We performed a systematic neurophysiological evaluation of newborns-infants newly diagnosed with congenital hypothyroidism and started on replacement therapy, in order to document the maturation of visual, auditory and somesthetic pathways and to evaluate the influence of treatment. Twenty-one patients (9 boys, 12 girls) were studied. They underwent neurophysiological evaluation consisting of visual, auditory, and somatosensory evoked potentials at diagnosis, as well as 6 and 12 months after initiation of treatment. At the time of diagnosis, 47.61 % of the patients had abnormal evoked potentials, with visual evoked potentials being most commonly abnormal. Twelve months after the onset of treatment, abnormal evoked potentials were detected in 33.3 % of the patients. In newly diagnosed infants with congenital hypothyroidism there is a high relevance of abnormal evoked potentials (47.61 %) at the time of diagnosis, declining with time and not correlating with the severity of the disease at diagnosis, the time of diagnosis or the initial dose of thyroxine.