Voice characteristics were studied before and after thyroidectomy in patients with intact vocal fold motility. The speaking voice was acoustically analysed in 47 patients and phonetograms were made in 17 patients. Eight parameters were measured and the pre- and postoperative values compared. The results show that the most affected parameter was the pitch of the speaking voice. The fourth postoperative day there was, on average, a lower SFo and a smaller Fo range during speaking. Postoperatively a progressive normalisation took place. After three months there were no more statistical differences and, looking at the individual measures, the SF0 of all patients fell within 2 semitones from their preoperative level. Vocal quality was also altered in the first postoperative examination, as shown by the higher jitter and smaller harmonics. These measures normalised after two weeks. In the same way, the evaluation of the limits of the voice by means of the phonetogram, showed that the maximal performances in the intensity and pitch domain were decreased in the earliest postoperative period. Information about temporary voice change is useful in patients undergoing thyroidectomy.