In the present study the survival of Escherichia coli O157:H7 in yoghurt produced at two different initial pH levels was investigated. Samples were contaminated with two different doses of E. coli O157:H7 (10(3) cfu/mL and 10(5) cfu/mL). Yoghurt samples were taken from incubation at pH 4.0 and 4.6. Incubated samples were stored at 4 degrees C for 14 days. In the samples, viable counts of E. coli O157: H7, pH and titratable acidity were determined on day 0 and the 1(st), 2(nd), 4(th), 6(th), 8(th) and 14(th) days of storage. E. coli O157: H7 survived in yoghurt produced at pH 4.0 and 4.6 in the both contamination level. The survival of E. coli O157: H7 was significantly lower at pH 4.00 than at pH 4.60 (P < 0.001) and at 10(3) cfu/mL than at 10(5) cfu/mL contamination level (P < 0.001).