The performance of the Rydel-Seiffer graduated tuning fork was examined in healthy subjects and in various groups of diabetic patients in order to evaluate its efficacy for identifying patients whose loss of vibration sensation may expose them to the risk of foot injury. Vibration perception score measured with the tuning fork declined with age (p less than 0.001) in the control subjects. It correlated well (r = -0.90, p less than 0.001) with the thresholds obtained with an electromagnetic instrument (Vibrameter) in diabetic patients, in whom vibration perception score was impaired compared with control subjects (4.0 +/- 1.8 (+/- SD) vs 5.4 +/- 1.4, p less than 0.001). Age-related Rydel-Seiffer tuning fork vibration sensation was impaired in 79% of 38 ulcerated feet of 26 patients. The tuning fork score was less than or equal to 4.0 in 95% of the ulcerated feet. We conclude that the Rydel-Seiffer graduated tuning fork is a suitable tool for screening for sensation loss and that diabetic patients with a tuning-fork score of less than or equal to 4.0 are vulnerable to ulceration.