Diabetic neuropathy is a common and troublesome complication of diabetes mellitus. Vibration sensation is a measure of large fiber nerve conduction, which is very commonly affected in diabetes. The present study addresses the question of whether vibration perception threshold (VPT) measurement using a biothesiometer is reproducible under different levels of blood glucose at different hours of the day. Seventy-five diabetic patients, 31 insulin-dependent diabetes mellitus and 44 non-insulin-dependent diabetes mellitus, with mean age 50.33 +/- 14.22 years (21-70 years) and diabetes duration of 14.3 +/- 10.6 years (1-60 years) were included in the study. Forty-one patients were male and 34 were female. In conclusion, VPT was found to be reproducible under different blood glucose levels at different hours of the day, which is affected only by the height of the patient. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.