ABSTRACT¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬INTRODUCTION: Due to increased demand and consumption of bottled water in Kathmandu valley, there has been a growing concern about the microbiological quality of this product. The objective of this study was to assess the microbial contamination of heterotrophs and total coliform.MATERIALS AND METHODS: This cross sectional study was done in randomly selected 30 different commercial brand of bottled water available in commercial market of Kathmandu valley, Nepal. Total coliform and heterotrophic bacteria were enumerated by the membrane filtration and spread plate technique, respectively.RESULTS: 90% (n=27) samples showed the heterotrophic bacterial count above the acceptable range (<50 cfu/ml) and 63.3% (n=19) samples showed the total coliform count crossed the WHO guidelines (0 cfu/ml). 90% (n=27) brands of bottled water were not safe for drinking as they exceed the heterotrophic count and/or total coliform count above the standards.CONCLUSIONS: The presence of heterotrophs and the coliform in the bottled water is a serious concern for public health. Concerned authority should prioritize this issue and continuously monitor the quality of mushrooming bottled water manufacturers in Kathmandu valley to provide safe drinking water to the population

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