The contamination of drinking water by waterborne pathogens is a serious public health concern. Thus, it is important the microbiological quality of drinking water. Our aim in this study was to investigate the samples of polycarbonate carboy water used as alternative drinking water in terms of pathogenic bacteria in Istanbul. Between May 2005 and May 2006, we collected a total of 92 polycarbonate carboy (19L) water samples from water selling points in different district. The samples were examined by membrane filtration method, and the results were evaluated according to the standardization of Turkey (TS 266) (Regulation Concerning Water Intended for Human Consumption). In these samples, 54 % coliform and 3 % faecal E. coli were found. Additionally, 23 % Aeromonas and 38 % Pseudomonas sp. were determined.pathogen bacteria such as enteropathogenic E. coli (EPEC), Salmonella, Shigella, Yersinia, Campylobacter, Vibrio and Plesiomonas sp. were not detected. In conclusion, it was observed that 55 % of polycarbonate carboy water samples are not safe according to TS 266. It is thought that the cause of this contamination is partially the carboys used repeatedly, therefore, disposable packages/bottles will be more convenient to check the contamination of this water.