Sclerotherapy (Sklehr-oh-THEHR-uh-pee) is a method of treating varicose and spider veins by injecting either a saline- (SAY-leen) or detergent-based solution which causes the vessel to close. Gradually, the treated vein is absorbed and disappears, and the blood is re-routed to healthy veins. Sclerotherapy has been in use since the 1930's and in many cases, is still the preferred technique for addressing problem veins. The procedure requires little or no anesthesia, can be done on an outpatient basis, and usually costs less than laser or surgical methods. Generally, all sizes of varicose veins may be treated with sclerotherapy. Often, even small veins can be injected successfully, if the doctor is experienced in working with these tiny vessels. Injections usually begin with larger veins that are highest on the leg and progress towards the ankle. To some degree, the outcome of sclerotherapy depends the skill of the physician involved. Most people will see a 50 to 80 percent improvement after the first round of injections. To achieve optimal results, two or three sessions may be needed. After the final treatment, the veins will continue to slowly improve over a period of weeks or months.