Unilateral vocal fold paralysis may cause incomplete closure of the glottis and a poor voice. Thyroplasty is a relative new operation to improve the voice by 'medialization' of the paralysed vocal fold. In our series of 29 patients 24 (83%) were satisfied and 26 (90%) had a better voice. After the operation the voice was louder, clearer and easier to understand. The dynamic and melodic ranges on the phonetogram were wider; maximum loudness and maximum phonation time were improved. There were no complications during the follow-up of 4 months to 5 years. In the three patients whose voice was not improved, the vocal fold paralysis was due to local trauma and scarring.