Sclerotherapy is an effective treatment option in low-flow vascular malformations (LFVM). Particularly in venous malformations, it can be considered a first-line treatment, while in lymphatic malformations (LM), surgery also has a major role. With introduction of Bleomycin electrosclerotherapy (BEST), the efficacy and safety of treatment appears to further improve. So far, there is no ideal sclerosing agent and all agents have their own safety profile. Currently picibanil and doxycycline are the most commonly used sclerosants in lymphatic malformation, while STS 3% and many others are used in venous malformations. If performed carefully and adjunct measures, e.g., for prohibiting rapid drainage of a lesion, are used as treatment efficacy of more than 70% is regularly achieved. Nevertheless, repeated treatments over the course of disease are required.