BACKGROUND Sclerotherapy involves the injection of a sclerosing agent for the elimination of intracutaneous, subcutaneous, and transfascial varicose veins. OBJECTIVE To update guidelines for sclerotherapy of varicose veins. METHODS The guidelines for sclerotherapy of varicose veins of the German Society of Phlebology were updated and modified through a review of the available literature. RESULTS Published clinical series and controlled clinical trials provide evidence to support the elimination of intracutaneous and subcutaneous varicose veins using sclerotherapy. Allergic skin reactions occur occasionally as allergic dermatitis, contact urticaria, or erythema. Anaphylaxis is rare. Transient migraine headaches present more frequently in patients treated with foam sclerotherapy than liquid sclerotherapy. CONCLUSION Sclerotherapy is the method of choice for the treatment of small-caliber varicose veins (reticular varicose veins, spider veins). If performed properly, sclerotherapy is an efficient treatment method with a low incidence of complications. BioForm Medical provided financial support for formal formatting of this manuscript without any influence over the content of the manuscript. The authors have previously participated in two scientific studies with polidocanol (ESAF and EASI study) financed by Kreussler.