To assess the clinical utility of 123I-metaiodobenzylguanidine (MIBG) scintigraphy in evaluating cardiac sympathetic nerve disturbance in diabetic patients, we performed MIBG scintigraphy in 18 diabetic patients and 11 normal controls. Diabetic patients with symptomatic neuropathy (DM2) had a significantly lower heart to mediastinum uptake ratio than did those without neuropathy or normal controls in initial and delayed images (initial image, 1.90 +/- 0.27 vs 2.32 +/- 0.38, 2.41 +/- 0.40, p< 0.01; delayed image, 1.80 +/- 0.31 vs 2.48 +/- 0.35 2.56 +/- 0.28, p < 001, respectively). Defect score, assessed visually, were higher in DM2 patients than in patients in the other two groups (initial image, 7 +/- 2.6 vs 1.5 +/- 1.9, 0.7 +/- 0.9; delayed image 10.6 +/- 3.3 vs 4.0 +/- 2.5, 1.7 +/- 1.6 p < 0.01, respectively). The maximum washout rate in DM2 patients was also higher than those in patients in the other two groups. The findings of these indices obtained from MIBG scintigraphy coincided with the % low-frequency power extracted from heart rate fluctuations using a power spectral analysis and the results of the Schellong test, which were used to evaluate sympathetic function. These results suggest that MIBG scintigraphy may be useful for evaluating cardiac sympathetic nerve disturbance in patients with diabetes.