The intraperitoneal infection of mice with previously titered doses of staphylococci has been found to regularly induce the formation of the foci of inflammation in the kidneys of mice, from which staphylococcal cultures has been obtained by the inoculation of the kidney material for 8 days (the term of observation). The use of this model has made it possible to carry out the dynamic study of structural changes in the populations of staphylococci by studying the biological properties of 100 subcultures isolated from the kidneys of the infected animals dissected every 24 hours. A decrease in the heterogeneity of the initial population, occurring due to a drop in the number of clones with hemolytic activity, lecithinase activity and smooth variants, has been registered. Thus, the proposed model permits the study of changes in the clonal structure of the populations of the infective agent, appearing under the influence of the protective capacity of the body in the dynamics of the infectious process.