Although sclerotherapy is an established procedure to treat ectatic veins, a wide disparity remains in the reported rates of success, especially for larger varicose veins. This article reviews the venous anatomy of the lower extremity and outlines the indications for sclerotherapy. The historical basis for treatment techniques is explored. The mechanism of action of sclerotherapy is discussed as a basis for treatment guidelines. If the procedure is properly performed, when appropriately indicated, rates of success should approach 100%.