To evaluate the effectiveness and long-term follow-up results of superselective adrenal arterial embolization (SAAE) of aldosteronomas.Thirty-three patients with unilateral aldosteronomas were treated with SAAE. A 0.2-7.0-mL dose of high-concentration ethanol (HCE) was selectively infused into the feeding arterial branches of the aldosteronoma through a microcatheter by using a coaxial technique. Hormone, electrolyte, and blood pressure levels were evaluated after SAAE. The influence of background factors on SAAE success rate and the influence of age on hypertension in the patients in whom SAAE was successful were assessed with the Fisher exact test and a logistic regression model.SAAE was successful in 27 (82%) of 33 patients. SAAE success rate was not influenced by sex, age, hypertension duration, family history of hypertension, adenoma site, type of ethanol used, or number of embolized arteries. The destructive effects of SAAE continued for the 6-94-month (mean, 45 months) follow-up period in all patients in whom SAAE was successful. In one patient, aldosteronoma recurred 15 months after SAAE and the second SAAE was successful. Blood pressure decreased in all 11 (100%) patients aged 45 years or younger and in eight (50%) of 16 patients older than 45 years (P =.008). Blood pressure decreased within 4 weeks after SAAE in 15 (79%) of these 19 patients. The rate of blood pressure reduction after SAAE decreased with increasing age, and the correlation was significant (P =.022). None of the 33 patients had severe complications.SAAE with HCE is an effective therapy for aldosteronoma.