Chronic renal failure (CRF) patients on dialysis frequently show reduced heart rate variability (HRV), which has been reported to be corrected by renal transplantation. Recently, (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy has been used to evaluate cardiac sympathetic innervation, and uremic patients often show marked abnormalities of cardiac (123)I-MIBG uptake. We investigated whether renal transplantation can improve cardiac (123)I-MIBG uptake in patients with CRF on dialysis. METHODS: We analyzed time- and frequency-domain measures of 24-h HRV and cardiac (123)I-MIBG scintigraphy before and 1-3 mo after renal transplantation in 13 CRF patients on dialysis and in 10 control subjects. RESULTS: Both 24-h HRV and cardiac (123)I-MIBG uptake were significantly abnormal in the patients before transplantation compared with the control subjects. After transplantation, (123)I-MIBG washout rate from the myocardium significantly decreased from 46% +/- 21% to 20% +/- 22% (P = 0.006), and the heart-to-mediastinum ratio of (123)I-MIBG uptake in the late image significantly increased from 1.74 +/- 0.39 to 2.06 +/- 0.39 (P = 0.006). On the other hand, HRV measures tended to increase after transplantation but the changes did not reach statistical significance (P > 0.05). CONCLUSION: Renal transplantation provides the improvement of uremic cardiac sympathetic neuropathy assessed by (123)I-MIBG imaging, which may be a more sensitive or at least an earlier marker than HRV.