Some patients who have undergone adenotonsillectomy (AT) or tonsillectomy(T) complain of voice change. Research was designed to determine the relationship between subjective voice change and change of parameters in boice analysis and to find the degree of voice change according to age and excised tissue volume. In 34 patients who underwent AT and 17 patients who underwent T, we measured the masalance, the fundamental frequency of /a/phonation and the formants and bandwidths of /a/, /i/, /u/ phonations. These parameters were measured preoperatively and also 7 days after the operation. Excised tissue volume was measured on operation. Postoperative changes were statistically analyzed. Any subjective voice change was asked to be reported at the visit 7 days after the operation. There was analysis for the difference of above parameters between some who answered "voice change" (A group) and the others who answered "no voice change" (B group). 24 patients(71%) who underwent AT and 4 voice change. Nasals nasalance change is an important factor in subjective voice change after AT.