Twenty neurophysiological parameters were employed to evaluate the presence and the degree of peripheral neuropathy (PNP) in a cohort of 135 patients (pts) on regular dialysis treatment (RDT) for 2 to 184 months. The 135 pts were divided into 3 groups according to the duration of RDT (group I: 52 pts with less than 5 yrs; group II: 46 pts 5 to 10 yrs; group III: 37 pts 10 to 15 yrs). Each group was then divided into two subgroups according to age (less or more than 47 yrs) to evaluate the influence of age on PNP. Correlations of electrophysiological parameters with some biochemical parameters (urea, creatinine, PTH) were looked for. The presence of clinical PNP was evaluated according to the Bolton classification: in group I, 50% of pts have mild PNP; in group II, 45.7% of pts have mild PNP; in group III, 81.1% have mild, 10.8% have moderate and 2.7% of pts have severe PNP. In as many as 84.4% of the 135 pts at least one of the 20 parameters studied had abnormal values and in 63% two or more parameters were abnormal. Of 20 parameters evaluated separately in the 3 groups only three showed abnormal mean values: sural nerve latency in all 3 groups; sural nerve Sensory Conduction Velocity (SCV) and peroneal nerve Max. Motor Conduction Velocity (MCV) in group III. Five parameters referring to ulnar nerves and two referring to the sural nerve were significantly more impaired in the group of pts with the longest duration of RDT and in this group the impairment was more severe in older patients.(ABSTRACT TRUNCATED AT 250 WORDS)