1. The effect of propofol on arterial tone in hypertension is poorly understood. We examined the effect of increasing concentrations of propofol (5.6 x 10-8 to 2.8 x 10-3 mol/L) on isometric tension developed by noradrenaline (10-7 mol/L)-contracted aortic rings from 12-week-old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). 2. In both WKY rats and SHR, propofol induced a dose-dependent inhibition of contraction induced by noradrenaline, but the amplitude of relaxation was larger in the SHR than in WKY rats. 3. The effects of propofol was endothelium independent in WKY rats, whereas in SHR relaxation induced by propofol was greater in endothelium-intact than in endothelium-denuded rings. 4. In conclusion, we found significant differences in the effect of propofol in hypertensive rats, which may be related to differences in structural and functional properties of the arterial wall observed in hypertension.