A neurophysiological (SEP, VEP) follow-up study was carried out in 30 diabetic patients with type I diabetes mellitus of ten or more years duration. This in order to investigate whether one year of improved glucoregulation may influence the progression of central damage. In our series, patients showed a significant decrement of HbA1C levels (p < 0.05) in the one-year follow-up. In the same period the frequency of SEP and VEP abnormalities varied from 10/30 (33%) to 16/30 (53%) and from 8/30 (26%) to 5/30 (16%) respectively. This finding would suggest that prevailing glycaemic control would be a major determinant for the outcome of VEP measurements. SEP alterations, in contrast, tend to progress in a 12 months period despite a considerable improvement in glycaemic control. However, by dividing patients in two groups according mean one year HbA1C less than 8% and more than 8%, the latter group only showed a significant increasing of absolute latencies of each median and tibial SEP components. Our results suggest that VEP abnormalities are still reversible in diabetic patients with improved metabolic control. The acquired abnormalities of somatosensory pathways persist longer, but a strict glycaemic control may influence and retard the progression of central conduction involvement.