One type of commercial cholesterol-free, reduced-calorie mayonnaise (CFM) made with different levels of acetic acid, was evaluated determine the survival characteristics of Salmonella typhimurium, Listeria monocytogenes F5069 serotype (4b) and E. coli O157:H7. Three formulation of CFM made with 0.3, 0.5 or 0.7% acetic acid in the aqueous phase were evaluated. The initial pH of the products after Assuit Vet. Med. J. Vol. 52 No. 109 April 2006 equilibration ranged from 3.9 to 4.1 which were adjusted by addition of HCL. Products were inoculated separately with 3 strains of Salmonella typhimurium, Listeria monocytogenes and E. coli O157:H7 respectively; at Ca 106 cfu/g and held at 23.9°C for up to 2 weeks. Listeria monocytogenes survived longer than E. coli followed by Salmonella in equivalent preparation of mayonnaise. . No Salmonella was detected at 48 h in mayonnaise made with 0.7% acetic acid in the aqueous phase. No Listeria monocytogenes was detected at 14 days post-inoculation in CFM made with 0.7% acetic acid, also no E. coli O157: H7 was detected at 5 days after CFM inoculation at the same level f acetic acid. Results indicated that these new varieties of mayonnaise when formulated with 0.7% acetic acid in the aqueous phase will inactivate >10° Salmonella and >10 . >104 cfu/g of Listeria monocytogenes and E. coli O157: H7 respectively within 48 h. holding time required for regular mayonnaise made with un pasteurized eggs. Hence, properly acidfied (pH<4.1) reduced-calorie mayonnaise containing 0.7% acetic acid in the aqueous phase is a microbiologically safe product.