Objective. To determine if MR plays a role in the initiation and development of cold-induced hypertension (CIH) by testing the hypothesis that RNAi inhibition of MR attenuates CIH. Methods. Recombinant adeno-associated virus (AAV) carrying a short hairpin small interference RNA for MR (AAV.MRshRNA) or a scrambled sequence (AAV.controlshRNA) was constructed. Six groups of albino mice were used (6 mice/group). Three groups were exposed to cold (6.7°C) while the remaining three groups were kept at room temperature (RT, warm) as controls. In each temperature condition, 3 groups received an intravenous injection of AAV.MRshRNA, AAV.ControlshRNA, or virus-free PBS, respectively, prior to exposure to cold. The viral complexes (0.35x1011 particles/mouse, 0.5 ml) or PBS (0.5 ml) were delivered into the circulation via the tail vein. Results. Blood pressure (BP) of the mice treated with AAV.ControlshRNA or PBS increased significantly during exposure to cold whereas BP of the cold-exposed AAV.MRshRNA-treated mice did not increase and remained at the level of the control group kept at RT. Thus, AAV delivery of MRshRNA prevented the initiation of CIH. AAV.MRshRNA significantly attenuated cardiac and renal hypertrophy. MRshRNA decreased the cold-induced increase in MR protein expression to the control level in hypothalamus, kidneys and heart, indicating effective prevention of the cold-induced up-regulation of MR. RNAi inhibition of MR resulted in significant decreases in plasma level of norepinephrine, plasma renin activity, and plasma level of aldosterone in cold-exposed mice. Conclusion. MR played a critical role in the initiation and development of CIH. AAV delivery of MRshRNA may serve as a new approach for prevention of hypertension.