Result of bacterial study on Oral Rehydration Solution (ORS) prepared in plain unboiled and boiled drinking water of Kathmandu valley is reported. Of the total 100 water samples collected from different sources and area all the samples, as a base line study, were subjected for the examination of bacterial presence. Eighty eight percent of the water samples studied were found to be unsatisfactory for drinking. Thirty five percent of the ORS prepared in unboiled water and kept for 24 hours at room temperature showed increased bacterial count whereas none of the ORS prepared in 5 minute boiled water and kept for 24 hour at room temperature showed any bacterial growth. Decreased bacterial count was not found in any of the ORS prepared in unboiled water. Typical coliform bacilli were found grown in 57.0% of the ORS prepared in unboiled water samples.