OBJECTIVE: This study investigated the relationship between autonomic nervous function and early renal dysfunction in elderly patients with mild-to-moderate essential hypertension (EH). DESIGN: A total of 223 elderly patients with mild-to-moderate EH were enrolled. Urinary albumin excretion (UAE) and urinary creatinine (UCr) were measured in all elderly patients with mild-to-moderate EH, and urinary albumin to creatinine ratio (ACR) was calculated (ACR = UAE/UCr x 0.113). All patients were divided into two groups such as ACR normal group (109 cases) and abnormal ACR group (114 cases) according to the results of ACR. Synchronic 24-hour ambulatory blood pressure monitoring and 24-hour ambulatory electrocardiogram were detected for all patients to simultaneously monitor heart rate variability (HRV) and blood pressure variability (BPV). RESULTS: The level of 24-hour SSD, dSSD, and nSSD and 24-hour PP (parameters of BPV) increased significantly (P < 0.028, P < 0.023, P < 0.027 and P < 0.019, respectively), while the level of RMSSD, pNN50, SDNN, and SDANN (parameters of HRV) decreased significantly(P < 0.048, P < 0.029, P < 0.025 and P < 0.022, respectively) in abnormal ACR group than in normal ACR group. Multiple logistic regression analysis showed that ACR was closely correlated with 24-hour SSD, 24-hour PP, SDANN, and SDNN (ss = 1.261, P = 0.000; ss = 1.121, P = 0.003; ss = -1.741, P = 0.000 and ss = -1.231, P = 0.002, respectively). CONCLUSIONS: HRV (SDANN, SDNN) and BPV (24-hour SSD, dSSD, nSSD) were significantly correlated to ACR in patients with mild-to-moderate EH. This result suggested that sympathetic activation was closely related with early renal dysfunction in elderly patients with mild-to-moderate EH.