In the process of revision of the WHO Guidelines for Drinking Water Quality, the need for a fundamental change in the guidelines for microbial safety has been identified. The former Guidelines were focussed on end-product monitoring for E. coli. This system is reactive; the warning signal is received at the time that the consumer’s health is already at risk. Outbreaks of disease through drinking water that meets this Guideline have been reported. This also indicates that meeting the Guideline is not always a safeguard against transmission of illness through that same drinking water. Developments in microbial risk assessment and in a risk management framework in the food industry have indicated that a preventive, risk based approach can provide the necessary expansion of the current approach to protect the consumer against health effects from drinking water.