Biostim is an immunomodulating agent of biologic origin indicated for the prophylactic treatment of recurrent respiratory tract infections in adults and children over one year of age. It has been proved effective by double-blind placebo-controlled trials. This study was undertaken to evaluate the value and tolerance of Biostim in a large number of patients under the conditions of actual use. Three thousand and eight patients were included in the study. At inclusion, 93.7% of patients had a history of recurrent ENT infections (6.27 +/- 3.04 episodes during the previous year). After three months follow-up, results were considered good by the investigator in 75.8% of cases; 75.3% of the children had either no infection or only one infection during the three months follow-up. Results were not influenced by age and/or a history of allergy.