Levamisole was tested double-blind in 106 children with recurrent upper respiratory tract infections. They received either levamisole (n = 53) or placebo (n = 53) 0.5 ml/kg bodyweight b.i.d. for two consecutive days each week for six months. A control examination was performed every two months. Both groups were compared by means of the Fisher-test and the Mann-Whitney U-test (two-tailed probability each). Improvement was observed more frequently in the levamisole group with regard to the number of episodes of infection, and the total duration and severity of the infections. No side-effects, except for some stomach complaints in one levamisole patient, were reported.