Neurophysiological studies of diabetic patients may show abnormalities even when clinical examination has revealed no sign of neuropathy. Quantitation of sensory function provides additional information when examining a patient with neuropathy. The value of the Hoffmann (H) reflex was investigated in diabetics who had undergone this examination. H-M intervals of the H-reflex, vibration perception thresholds (VPT's) and thermal discrimination thresholds (TDT's) were determined in 34 diabetics with clinical evidence of neuropathy and 16 diabetics without symptoms or signs of neuropathy. Normal values for VPT and TDT were obtained from the examination of 40 healthy subjects. The values of the H-M interval were significantly correlated with VPT's and not with TDT's. Three patients with clinical evidence of neuropathy and abnormal VPT's and TDT's had normal H-M intervals. For research purposes it is recommended that H-reflex studies are combined with the determination of sensory thresholds, but from a practical point of view determination of the H-M interval proved to be an effective tool for the investigation of neuropathy in diabetic patients.