The purpose of the present guidelines on the (131)I therapy of benign thyroid disorders formulated by the European Association of Nuclear Medicine (EANM) Therapy Committee is to provide advice to nuclear medicine clinicians on how to treat benign thyroid conditions employing optimal (131)I activities. The recommendations were formulated based on recent literature and expert opinion regarding rationale, indications and contraindications for the use of (131)I procedures, as well as the adequate (131)I activities in different thyroid disorders, and the administration and patient preparation techniques to be used. Recommendations are also provided on history and examinations before (131)I therapy, patient counselling and precautions associated with (131)I therapy. Furthermore, potential side effects and alternative treatment modalities are reviewed. Special attention is paid to these aspects in the treatment of children undergoing this procedure.