The static or dynamic stretch of helical strips or sudden increase of the transmural pressure produced contraction in cerebral and coronary arteries isolated from dogs and rabbits. The simultaneous recording of Ca transients and contractile activity showed that fluorescence intensity of fura-2 loaded cerebral artery increased during stretch activation. The contractile activation due to stretch was augmented by potentiators of Ca2+ influx, while it was attenuated by inhibitors of Ca2+ influx. The results suggest that contractile activation by mechanical stretch seems to provide a useful alternative technique to electrical and pharmacological stimuli for use in studies on contraction of vascular tissues and the effects of drugs and ions such as Ca antagonists and divalent cations which affect Ca2+ movement.