SUMMARY: It was found that Staphylococcus aureus usually survived within monoeytes of normal rabbits for several hours without multiplication, but were eventually destroyed. However, there was variation in the intracellular behaviour in leucocytes of different rabbits in that cells from some donors began the slow destruction of the staphylococci shortly after phagocytosis. In many of these experiments streptomycin was incorporated in the tissue-culture medium to suppress the extracellular multiplication of staphylococci. Interference by streptomyein with the intracellular be-haviour of staphylococci was considered as minimal on the basis that the intra ellular survival was not influenced by different concentrations of the drug in the tissue-culture medium nor did incubation of the cells in the antibiotic before infection alter the subsequent survival of the organisms.