Associated adenoviral, staphylococcus, and streptococcus infection was studied in the cultures of cells HEp-2 and PAO. Under conditions of monoinfection the cell culture largely inhibited the reproduction of staphylococci, and failed to influence the streptococci. In double and triple associated infections staphylococci overcame the inhibitory action of the cell culture. The pathogenic properties of cocci (plasma coagulation, hemotoxic properties) grown in the cell culture both under conditions of monoinfection, and in associations, failed to change. In double and triple associated infections adenoviruses did reproduce, but in lower titre than in monoinfection. Under conditions of mixed infection cocci penetrated and reproduced in the cell cytoplasm more intensively than in monoinfection. The cytopathic action was determined by viral associate, and was identical by its character to adenoviral monoinfection. A statistically significant increase in the activity of aldolase and transaminase enzymes was noted in mixed infection. The changes in the enzyme activity proved to depend on the character of the associations studied.