The purpose of this study was to evaluate the effectiveness of 5% trichloroacetic acid (TCA) in the treatment of acute external otitis (AEO) in comparison with standard clinical treatment. All patients who consecutively presented in our emergencies with AEO during the summer months of the previous year were included in the study. They were randomly divided into two groups: the study group included 117 patients treated with TCA and the control group included 98 patients treated with eardrops containing antibiotic and corticosteroid. Occasionally, an antibiotic was administered orally for 7 days, in severe cases of AEO. All patients were evaluated on days 1, 3, 5, 7, and 10, whereas another review appointment was given 20 days later. Outcome measures included evaluation of efficacy using a six-step infection score and tolerability by visual analog scale. Additionally, adverse reactions, complications, and recurrences were recorded. Treatment was successful for all patients of the study group, whereas 8 failures were found in the control group. The infection score improved faster in the study group than in the control group, resulting in an earlier clinical cure (mean 4.1 and 8.6 days, respectively). Tolerability was significantly better in the study group, on all points of evaluation. Complications and adverse reactions were minimal in both groups. Our results show that TCA is a very effective and non-toxic agent for the treatment of AEO. Rapid pain relief and prevention of recurrences are its main advantages.