In 46 children with acute laryngitis the authors tested the state of cellular immunity in the acute stage and repeatedly during controls after 1-3-month intervals. They assessed the number of total T lymphocytes and active T lymphocytes, the number of B lymphocytes and by means of the test of blastic transformation they obtained information on the functional fitness of the T lymphocyte population. They revealed important changes in the state of the T lymphocyte population, i.e. quantitative as well as functional changes which persisted in 80% of the children 1 and a half months after the acute state. This finding must be considered the consequence of viral infection potentiated by corticoids which may be the cause of prolonged morbidity of these children. It is not advisable to admit these children to child communities. In case of repeated respiratory diseases it is recommended to make an immunological examination and apply immunomodulating therapy in immunodeficiencies.