The therapy of varicose veins is multimodal and depends on the individual clinical findings. In addition to compression therapy, invasive approaches for elimination of reflux for the treatment of varicose veins are available, such as surgical and interventional methods and sclerotherapy. The administration of a sclerosing agent into a varicose vein results in an occlusion of the treated vein. Recently the use of foam sclerotherapy had a renaissance. Several studies have documented the efficacy of foam sclerotherapy in selected patients. The possibility of treating patients in an outpatient setting, with low costs and rapidly, makes foam sclerotherapy very attractive compared to invasive and minimally invasive methods. However long-term follow-ups in properly controlled randomized trials are needed before foam sclerotherapy can be recommended as a routine procedure. This paper introduces the method and the treatment possibilities with foam sclerotherapy in chronic venous insufficiency.