Thyroid adenoma is commonly associated with surgery and radiometabolic treatment; recently, according to previous successful reports, percutaneous ethanol injection therapy under sonographic guidance, has been introduced as an alternative. This technique has already been favourably used in the treatment of focal lesions, such as liver cancer and hyperparathyroidism. In our experience, we have treated with such therapy 69 patients affected by thyroid adenoma (55 females, 14 males; 28 pretoxic, 41 toxic). Ethanol (0.5-2.8 mL/mL nodular tissue) was injected, under sonographic guidance, in 4-9 sessions (1 weekly). Thyroid hormone profile was assessed during treatment and at 3 and 6 months follow-up. Apart from local transient pain in 21% sessions, two cases of pyrexia (38.5 degrees-1 day) and 3 cases of transient dysphonia, no relevant adverse effects were observed. A slight thyroid hormone increase was seen in both groups immediately following treatment. Six months after therapy a biochemical and clinical remission of hyperthyroidism was observed in 33 out of 41 toxic patients (80%); a significant increase of TSH levels was seen in both groups (p < 0.001). With follow-up, significant volume shrinkage (70-80% volume reduction--p < 0.0001) as well as structural alterations of the nodule, were consistently recorded at sonography, in both groups; a linear relationship (p < 0.0001) between pretreatment volume and volume reduction was found. At scintiscan functional activity of extranodular parenchyma was found in 75% of patients affected by pretoxic adenoma and in 63.1% of patients with toxic adenoma. These data confirm that percutaneous ethanol injection therapy is effective in obtaining functional ablation and in inducing remission of hyperthyroidism, when present; so it represents a valid and safe alternative to standard therapeutic tools of thyroid adenoma.