The effect of prolonged room environment (maximum 7 days) on several pathogenic properties of beta hemolytic streptococci was studied. The properties examined were (1) ability to grow in defibrinated human blood[long dash]2 Group A strains; (2) ability to lyse human blood clot[long dash]1 Group A strain; (3) ability to produce a skin toxin (rabbit)[long dash]1 Group A strain; (4) susceptibility to agglutination by homologous immune serum[long dash]Group C strain. Despite the fact that efforts were made to gauge minimal losses of pathogenic power no evidence was adduced that the properties of any of the strains were impaired by exposure to room environment.