The purpose of this study is to validate the generalizability of the efficacy and safety of radiofrequency (RF) ablation for treating autonomously functioning thyroid nodules (AFTN) in a large population multicenter study. Methods: This study included 44 patients from 5 institutions who refused or were not suitable for surgery or radioiodine therapy. Twenty-three patients were affected by a toxic nodule and 21 by a pretoxic nodule. RF ablation was performed using an 18-gauge, internally cooled electrode. Nodule volume, thyroid function, scintigraphy, symptom/cosmetic scores, and complications were evaluated before treatment and during each follow-up.