Abstract: The present invention relates to a dilatation catheter designed to be introduced into a canal of the body. The invention finds a particular application in the treatment of diseases of the coronary arteries. According to the invention, the balloon has an outer wall designed to come into contact with the inner wall of the body canal, while in the position of use, and an inner wall fixed in a tight manner to the outer wall to define therewith, while in the position of use, an inner annular cavity. The catheter further includes a support element shaped so as to hold the inner wall of the balloon, in the position of use, while allowing the body fluid to flow in the space between an inner element and the inner wall of the balloon.