Background: Determinacy of different variants of clinical course of the disease with functional condition of local mechanisms of immunological defence in one-year-old children in acute intestinal infections of Klebsiella etiology has been studied based on dynamics of the contents of secretory IgA in corpofiltrate. The diagnosis of acute intestinal klebsiellosis was confirmed with the results of bacteriological (repeated, at least twice, isolation of Kl. pneumonia from faeces in concentration 106 and more CFU/g) and the results of special immunological investigation (detection of antibodies in blood serum against Kl. pneumonia strains, isolated from faeces). Material and methods: Two groups of comparison have been formed for the study of relation between different variants of clinical course of acute intestinal klebsiellosis and functional condition of local immunity: the 1st group with acute cyclic and the 2nd group with continuous course of the disease. Results: It has been established that on admission to inpatient department (1-3 days of the disease onset) contents of secretory IgA in corpofiltrate markedly exceed analogous indices in healthy children, but do not differ. However, on further stages of dynamic monitoring in unhealthy groups a considerable difference of analysed indices was observed. Thus, in patients from the first group a marked increase in contents of secretory IgA, persistent on further stages of monitoring, in comparison with initial data was observed on the 4-5th days of treatment. Such type of reaction of local mechanisms of immunological defence indicates acute cyclic course of the disease. This type of reaction of local mechanisms of immunological defence clinically corresponds to cyclic course of the disease. In patients from the 2nd group in continuous course of the disease, a reliable increase in secretory IgA in comparison with initial data occurs only on the 8-10th days. Conclusion: Thus, initial indices of the contents of secretory IgA in corpofiltrate in acute intestinal klebsiellosis in one-year-old children are not informative for prognosis of further course of the disease. It is expedient to detect this index starting from the 4-5th days of treatment.