There is mounting evidence that increased oxidative stress and sympathetic nerve activity play important roles in renovascular hypertension. In the present study, we tested whether enhanced superoxide signaling in RVLM of 2 kidney-1 clip rats (2K-1C) contributes to the chronic hypertension via sympathetic activation in conscious rats. In our previous studies, we identified an increase in AT1 angiotensin II receptor expression and in oxidative markers within the RVLM of 2K1C rats. Furthermore, tempol or vitamin C acute administration into the RVLM or systemically reduced blood pressure and renal sympathetic activity in 2K-1C but not in control rats. Thus, in this study, we enhanced superoxide scavenging into the RVLM by overexpressing cytoplasmically targeted superoxide dismutase enzyme using an adenoviral vector (Ad-CMV-CuZnSOD) in Wistar rats (male, 150 to 180 g) in which the left renal artery was occluded partially 3 weeks earlier. Hypertension was documented using 24 hour radio-telemetry recording of arterial pressure (AP) and heart rate (HR) in conscious freely-moving rats. Hey Presto software (Waki et al, 2006) was used to calculate indices of autonomic function from the AP and HR variability by spectral analysis. Renovascular hypertension elevated both serine phosphorylation of p47phox subunit of NADPH and superoxide levels within the RVLM. The elevated superoxide levels were normalized by expression of CuZnSOD in the RVLM. Moreover, the hypertension produced in the 2K-1C rats was reversed 1 week after viral-mediated expression of CuZnSOD. This antihypertensive effect was maintained and associated with a decrease in the low-frequency spectra of systolic blood pressure variability, suggesting reduced sympathetic vasomotor tone. The expression of CuZnSOD was localized in the RVLM neurons, of which some contained tyrosine hydroxylase (C1 neurons). None of the above variables changed in control rats receiving Ad-CMV-eGFP in the RVLM. In renovascular hypertension, superoxide signaling in the RVLM plays a major role in the generation of increased sympathetic vasomotor tone and the chronic sustained hypertension.