In a double-blind controlled design, 7 patients with painful diabetic neuropathy received lidocaine 5 mg/kg or saline intravenously over a period of 30 min. Thermal sensibility quantified by thermotest was not affected by lidocaine. In 3 of the patients nociceptive flexion reflex thresholds could be determined. The threshold was increased by lidocaine and returned to pre-infusion level within 10 days. Lidocaine also increased the threshold in 4 healthy subjects, but did not affect the Hoffmann reflex. These results suggest that lidocaine exerts its pain-relieving effect on the spinal level in diabetic neuropathy.