This study was conducted to determine of microbiological quality and some chemical characteristics of 50 kefir samples purchased from different retail markets in Bursa province. In the samples investigated, the mean numbers of lactobacilli, lactococci, enterococci, Enterobacteriacea, Staphylococcus aureus and yeast were determined as 3.6x10(7) cfu/ml, 1.8x10(8) cfu/ml, 4.8x10(4) cfu/ml, 7.3x10(3) cfu/ml, 2.4x10(2) cfu/ml and 7.7x10(4) cfu/ml, respectively. 26 of 50 kefir samples were found to have <0.30 MPN/ml of total coliform while 5 samples had numbers of >110 MPN/ml. For remaining 19 samples, the average bacteria count was 5.3 MPN/ml. Escherichia coli was isolated from 11 (22%) of the samples. Mean acidity, fat and dry matter contents of kefir samples were found as 0.8 L.A.%, 2.3 % and 11.3 %, respectively, while the pH values varied between 3.9 and 4.7. Consequently, the microbiological findings showed the contamination of kefir samples with microorganisms including E. coli and S. aureus, well known as a remarkable bacterial pathogens, and thus possible health risks for consumers.