This project will provide a harmonised framework and scientific basis for quantitative microbiological risk assessment of drinking water. Via a source-to-tap approach all stages in drinking water production will be included. The information on these stages will be combined into a safety-assessment of the water that is consumed. Uncertainty analysis is used to determine the strengths and weaknesses of this approach. The outcome of the risk assessment is verified against the current knowledge on disease-incidence in Member States and data from outbreaks of waterborne disease. This approach has the benefit of providing water companies, regulators and consumers with insight in the level of consumer protection and the strength and weaknesses of the system installed to protect drinking water quality.