Vocal function was assessed in 15 patients who received thyroplasty type I for the rehabilitation of unilateral vocal fold paralysis. The function was assessed by perceptual evaluation, voice intensity and frequency range profiles, and questionnaire. Goals of the study were to evaluate the efficacy of thyroplasty in improving the voice, to compare postoperative thyroplasty voices to normal voices, and to correlate objective measurements to the results of the questionnaire regarding satisfaction with the voice. Perceptual evaluations were performed by randomizing normal and thyroplasty voices on a recording tape. The voices on the tape were then rated by independent, blinded, trained listeners. The perceptual qualities of pitch, intonation, and loudness were not statistically different than normals; however, voice qualities of strain, breathiness, hoarseness, harshness, and unsteadiness were different than normals. Mean frequency range and mean intensity range were moderately to severely reduced from normals with a wide variation being present in the results. The correlation between the higher threshold phonation pressures and decreased intensity ranges found in some patients is discussed. Questionnaire results indicated that a high degree of satisfaction with the surgery was present (92%). Extreme or general satisfaction with voice was present in 73%. The most difficult voicing was experienced at work, with 25% needing to adjust their employment to accommodate their voice abilities. These results indicate that thyroplasty type I is effective in partially rehabilitating unilateral voice fold paralysis. Voice function is still not normal, probably in part due to the underlying disease.