This study investigated longitudinal changes of vocal efficiency and stability after primary thyroplasty type 1. Fifty-three patients with unilateral vocal-fold paralysis underwent vocal-function evaluation preoperatively and at periodic intervals of 1, 3, and 6 months postoperatively. Vocal-function assessment included videostrobolaryngoscopic examination, acoustical and aerodynamic analysis, and perceptual judgment of voice characteristics. Parameters that included glottic-gap size, maximum phonation time, glottic-flow rate, jitter, harmonic/noise ratio, breathiness, hoarseness, loudness, and phrasing showed significant improvement after thyroplasty and remained stable as early as 1 month postoperatively, with only slight fluctuations over a 6-month period. Postoperative voice outcome was not affected by age, sex, duration of vocal symptoms, cause of paralysis, or preoperative pulmonary function.