The microbiological quality of fresh,Egyptian oysters collected from different markets in Ismailia and Cairo governorates were determined. The. mean values of aerobic plate counts incubated at 35°C was 1.8 x10' CFU/g. The mean of the as 
most probable numbers of coliforms and fecal coliforms was 235/g. The mean S. aureus count was 2.1 x 104/g. E. coli was found in 18 of 20 samples, while S.aureus, Salmonella and Vibrio parahaemolyticus were found in 14,1 and 3 of 20 
samples, respectively. The role of depuration processes on the bacterial load of- oysters was studied. E. coli was undetected after 24 hr, while aerobic count reached the eaten raw or very mildly cooked they seem
acceptable level after 48 hr. Coliforms, fecal coliforms, S. aureus were completely eliminated after .72hr., while Vibrio parahaemolyticus was still present even after three days of depuration.