The immunological cellular response was studied in 22 children aged between 5 and 10 years. One week before and one month after tonsillectomy, the mitogenic response to phytohaemagglutinin (PHA), concanavalin (ConA) and pokeweed mitogen (PWM) was tested. Our results showed statistically significant decreases in stimulation index (SI) to PHA, ConA and PWM after tonsillectomy. This suggests that the tonsils may influence the cellular immune status in children. The higher level of preoperative activity in children with recurrent tonsillitis could be understood as the result of stimulation of lymphocytes by bacteria.