Low flow vascular malformations, especially venous and macrocystic lymphatic malformations, are effectively treated by percutaneous intralesional injection of sclerosant drugs, such as ethanol and detergent sclerosant drugs. Good to excellent results are possible in 75%-90% of patients who undergo serial sclerotherapy. Most adverse effects are manageable, but severe complications can result from the intravascular administration of ethanol. It is generally recommended that the treatment of vascular malformations be performed in a multidisciplinary setting by practitioners with appropriate training and support.