Growth and survival of Escherichia coli O157:H7 inoculated (104 cfu/ml) into heat treated cow’s milk pre-and post-fermentation, in the presence of mastic oil (0.05 and 0.1% v/v) and almond oil (1 and 2% v/v) was investigated. Yogurt was prepared with the addition of a 2% (v/v) mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus and incubation at 45oC for 4 hr. Fermented yogurt samples were subsequently stored at 4oC for 10 days. After 24 hr post-fermentation the pH decreased from 6.9 to 4.1 stabilizing at this value until the end of storage. Starter culture LAB was not substantially affected by the presence of essential oils at the concentrations used. No Yeasts and Moulds were detected in the product throughout storage. In the case of pre-fermentation inoculation of E.coli O157:H7, the pathogen was unable to grow at the fermentation temperature of 45oC. When inoculated post-fermentation into yogurt, E.coli O157:H7 survived for approximately 8 days in control samples, 2 days with the addition of mastic oil (0.05 or 0.1%) or almond oil (2%) and 6 days with the addition of almond oil (1%). Thus, even though mastic and almond oil have a controlling effect on E.coli O157:H7 they do not completely eliminate the pathogen in stirred yogurt during the first few days of refrigerated storage.