This study evaluates the efficacy of autologous fat injection for medialization of the paralyzed vocal fold. In 21 patients with unilateral vocal fold paralysis, autologous abdominal fat was injected into the thyroarytenoid muscle to achieve medialization. All patients were followed up with serial videolaryngoscopy and voice evaluation. At 2 months' follow-up, the voice was judged to be excellent in 10 patients, slightly breathy but significantly better than the preoperative voice in 6 patients, and markedly breathy in 4 patients. At 3 to 4 months' follow-up, of the 10 patients with excellent results, 5 maintained an excellent voice, 3 had developed slight breathiness, and 1 had developed severe breathiness. Long-term (6 to 12 months) results were available in 11 patients, and all of them maintained the same voice quality that was noted during the 3 to 4 months' examination. Magnetic resonance imaging of the larynx was obtained in 7 patients at intervals ranging from 1 to 7 months and compared to the baseline scan obtained at 1 week postoperative to assess the amount of fat remaining in the muscle. The images showed fat volume to persist, but a decrease in the fat signal was observed over time. The results suggest that the duration of medialization with autologous fat is variable, but appears to last at least 2 to 3 months. This loss of volume after 3 months seems to be due to absorption of the fat and possibly muscle atrophy. Autologous fat injection is relatively safe and easy to perform, and is an ideal method of temporary vocal fold medialization in patients in whom return of vocal fold function is expected.