Transcutaneous electrical nerve stimulation (TENS) is one of the therapies for painful neuropathy. Its analgesic mechanisms probably involve the gate control theory, the physiological block and the endogenous pain inhibitory system. The aim of the study was to determine whether TENS improves small fibre function diminished because of painful diabetic neuropathy. Forty-six patients with painful diabetic neuropathy were treated with TENS three consecutive hours a day for 3 weeks. Treatment effect was evaluated with cold, warm, cold pain and heat pain thresholds, vibration perception thresholds and touch perception thresholds. In all patients, thermal-specific and thermal pain sensitivity determination showed quantitative and qualitative abnormalities in all the measured spots. After the TENS therapy, no statistically significant changes in cold, warm, cold pain, heat pain, vibratory perception and touch perception thresholds were observed in the stimulated area. TENS did not alter C, A[delta] nor A[beta] fibre-mediated perception thresholds. The observed changes at thenar are probably because of central mechanisms. In general, analgesic mechanisms of TENS are likely to be complex.