The authors report their experience on the therapeutic value, in terms of efficacy and tolerance, of percutaneous ethanol injection (PEI) in the treatment of autonomous thyroid nodules (ATN). A group of 15 patients, 13 in clinical pretoxicity and 2 in initial thyrotoxicosis, were submitted to fine-needle ethanol injection (95%) performed under US guidance. The amount of injected alcohol was measured on the basis of the volume and diffusion of alcohol itself within the nodule, in the whole of 79 injections given. Follow-up lasted 3-15 months. Thyroid scanning demonstrated a complete or partial recovery of extranodular parenchymal function in 80% and 20% of cases, respectively. In all cases a volume reduction greater than 50% was obtained, with an initial sharp fall, already after the first month, thanks to early alcohol cytotoxicity. In the 2 patients with toxic ATN serum, normal values of free hormones have been observed ever since the third weekly injection. Good tolerance to treatment was observed, and no permanent complications. In agreement with other authors, we believe our experience to show that PEI represents a new therapeutic approach in patients with ATN. PEI will certainly play a preferential role, relative to other conventional therapies, in the management of clinical pretoxic ATN, regarding which no uniform treatment protocol exists yet.