Activity and kinetic properties of tissue nonspecific alkaline phopsphatase and acid phosphatase were investigated in adenoids and tonsils of 62 children tonsiloadenoidectomised because of recurrent infection using p-nitrophenylphosphate as a substrate. Kinetic properties were calculated by the method of Levenberg-Marquardt. The mean value of tonsil TNAP activity was 3.525 U/mg of protein versus 7.280 U/ mg of protein in adenoids (t = 5.928, df = 60, p < 0.01). ACP activity was also significantly lower in tonsils (10.844 U/mg of protein) than in adenoids (13.059 U/mg of protein) (t = 11.318, df = 60, p < 0.01). There were no influence of age and sex to both enzyme activities. TNAP activity was significantly higher in hypertrophic (4.132 U/mg of protein) than in atrophic (2.531 U/mg of protein) (t = 2.361, df = 20, p < 0.05). Tonsillar TNAP was more effective than adenoid TNAP (t = 11.769, df = 60, p < 0.01). Results suggest the possibility that recurrent infection influences the tonsils more than adenoids and age. Hypertrophy could be an adaptive mechanism of palatinal tonsils during the infection.