Abstract: A dilatation catheter intended in particular for treatment of strictures in the carotid artery has at its front end a dilatation balloon, which is inserted in the folded state into the carotid artery and is inflated in order to widen the stricture. In front of the dilatation balloon a sealing balloon is arranged which serves to seal off the carotid artery downstream of the stricture, in order thereby to prevent a migration of any stricture material which may become detached during treatment, and thus to avoid the risk of an embolism. Between the dilatation balloon and the sealing balloon there is a draw-off and inlet opening through which, after widening and with the sealing balloon inflated, detached stricture material can be drawn off or washed away.