To produce a prolonged decrease in blood pressure, we have developed a nonpathogenic adeno-associated viral vector (AAV) with the antisense DNA for AT1-R. AAV has many advantages over other viral vectors. AAV does not stimulate inflammation or immune reaction. AAV enters nondividing cells and does not replicate. Therefore, it is an appropriate choice for gene therapy. Recombinant AAV was prepared with a cassette containing a cytomegalovirus promoter and the cDNA for the AT1receptor inserted in the antisense direction. The cassette was packaged in the virion. Stable transfection of NG108-15 cells with the pAAV-AS (plasmid AAV) antisense to AT1-R produced a significant reduction in AT1receptors. A single injection of the rAAV-AS (viral vector) was made in adult spontaneously hypertensive rats, either directly in the hypothalamus (1 micro Liter) or in the lateral ventricles (5 micro Liter). The result shows that there is a significant decrease of blood pressure ([nearly equal] 23 +/- 2 mm Hg) for up to 9 weeks after injection. Control injections of mock vector produced no change in blood pressure during the same time period in age-matched controls. In young spontaneously hypertensive rats (3 weeks), a single intracardiac injection of recombinant rAAV-AS reduced blood pressure and slowed the development of hypertension compared with controls (P < .01). The results suggest that a prolonged reduction in high blood pressure can be achieved with AAV vectors delivering antisense to inhibit AT1receptors with a single administration. (Hypertension. 1997;29[part 2]:374-380.)