We investigated the usefulness of the C64 quantitative tuning fork in assessing vibratory sensation in patients with diabetic neuropathy. The vibratory sensation scores determined by using the C64 quantitative tuning fork were significantly correlated with severity of subjective symptoms of numbness, cold, desensitization, spontaneous pain in the upper and lower extremities, and vertigo, as well as measurements of neurologic function (threshold of vibratory sensation, the coefficients of variation of the R-R intervals of the electrocardiogram at rest, and the motor nerve conduction velocity [MNCV] of the lower extremities; P < 0.05 to 0.01). Subsequently, we evaluated the effects of niceritrol on neurologic function in the same patients by using the C64 quantitative tuning fork, other neurologic function tests, and the change in severity of subjective symptoms before and after therapy. Niceritrol significantly improved measures of neurologic function (vibratory sensation scores, MNCV of the upper extremities, and sensory nerve conduction velocity of the lower extremities; P < 0.05 to 0.001), and subjective symptoms (numbness, cold, desensitization, and spontaneous pain in the lower extremities; P < 0.01 to 0.001). Our results suggest that the C64 quantitative tuning fork is a convenient and objective tool for assessing the severity of diabetic neuropathy and that niceritrol is useful for the treatment of this disease.