Abstract: A device for treatment of varicose veins includes a catheter (1), which can be inserted into a vein to be treated. There is a balloon (2) with at least one cutting element (3) for cutting at least part of an inner wall of the vein arranged on a proximal end (1a) of the catheter. The catheter has side openings (7a-7c), through which a sclerosing agent can be introduced into the vein. The at least one cutting element includes a cutting edge configured to cut intima and media of the vein when withdrawing the balloon from the vein after treatment with the sclerosing agent.