Forty-three patients with a diagnosis of unilateral vocal fold immobility underwent thyroplasty type I with the Montgomery Thyroplasty Implant System. Preoperative and postoperative evaluations were completed by means of videostroboscopic, acoustic, and aerodynamic measures. Clinicians' perceptions of vocal quality and patients' satisfaction with the surgery and vocal quality were determined. Improvements after surgery were observed for glottal closure, vocal fold amplitude, mucosal wave activity, average intensity, maximum intensity range, maximum phonation time, glottal airflow, average sound pressure, and subglottal pressure. Average postsurgical fundamental frequency values fell within normal limits and did not display significant changes relative to presurgical values. The clinicians' perceptual evaluations indicated an improvement in voice quality for most patients. A majority of patients expressed satisfaction with the surgery and resulting voice quality. The results of the present study, in combination with the surgical advantages that have been described for the Montgomery Thyroplasty Implant System, support the view that this approach offers an attractive alternative for treating unilateral vocal fold immobility.