Groundwater is the most preferred source of water in various user sectors in India on account of its near universal availability, dependability and low capital cost. The present study mainly focus on the drinking water quality index of one of the fast growing city of India, Patna. The city has a population of 58.3lakhs of people which mainly relay ground water for drinking. The ground water from fourteen stations was analysed. Even though the Water Quality Index (WQI) put the water into ‘good water’ category, none of the samples were found suitable because all the samples were found high concentration of total and faecal coliform. Alkalinity, Total Dissolved Solids (TDS) and Nitrate concentrations in some stations were found above the drinking water standards.