The aim of this paper is to report the results of a multicenter open randomized clinical study of the efficacy of nasal and nasopharyngeal irrigation for the prevention of seasonal morbidity due to acute respiratory infections (ARIs) in the groups of preschool and school children. A total of 2386 children attending secondary schools and 519 ones attending kindergartens were examined.. The study has demonstrated that irrigation of the nasal cavity and nasopharynx efficaciously reduces (by 2.4-3.2 times) the morbidity due to ARIs in organized children's collectives throughout the entire length of the epidemiological period; moreover, it improves the clinical course of ENT organ diseases and bronchial asthma.