The present experiment was carried out to study the effect of processing of yoghurt, and cold stor-age of both yoghurt and acidified milk on the sur-vival and growth of two reference strains. Esche-richia coli O157: H7 and Enterotoxigenic Staphylococcus aureus were inoculated into milk in low (103CFU/ml) and high levels (10°CFU/ml). The obtained results revealed that E. coli 0157: H7 showed slight increase in viable cell count cither at low or high concentration, while S,meus Showed gradual decrease in both low and 2 eis during processing of yoghurt. other hand the organisms showed another mi at storage temperature. In storedtal »£. coli 0157: H7 decreased grad-Y from 4.23 to 1.95 log CFU/g and by about 3°8 phase Mller 7 days of storage, then the organ-ism was completely disappeared after 10 and 25 days for low and high dose respectively. While in acidified milk the viable cell count of E. coli de-creased from 4.36 to 2.90 log CFU/g after 25 days of cold storage. §. aureus viable cell count was sharply decreased in stored yoghurt from 4.34 to 2.04 log CFU/g and from 7.17 to 2.11 log CFU/g after 3 and 10 days at low and high concentration respectively, while in acidified milk the organism showed a decrease in count from 4.39 to 1.69 log CFU/g after 15 days of cold storage. Changes inthe pH of the examined products were studied.The public health importance of the tested organ-isms and suggested control measures to improve keeping quality of yoghurt were discussed.