The study was carried out in Chandigarh, India with the following objectives: (1) to monitor the bacteriological quality of drinking water; (2) to collect data on bacteriological contamination of water collected at point of use; (3) to test both groundwater being supplied through hand pumps and pre-treated water; and (4) to determine the pattern of seasonal variations in quality of water. The community-based longitudinal study was carried out from 2002 to 2007. Water samples from hand pumps and tap water were collected from different areas of Chandigarh following a simple random sampling strategy. The time trends and seasonal variations in contamination of water according to area and season were analysed. It was found that the contamination of water was higher during the pre-monsoon period compared with the rest of the year. The water being used in slums and rural areas for drinking purposes also had higher contamination levels than urban areas, with highest levels in rural areas. This study found that drinking water supply in Chandigarh is susceptible to contamination especially in rural areas and during pre-monsoon. Active intervention from public health and the health department along with raising people's awareness regarding water hygiene are required for improving the quality of drinking water.