Drinking water meeting microbiological standards appears to be a significance source of gastrointestinal illnesses. Such an endemic situation can be related to the constant introduction of low level of pathogens and growth of heterotrophic microorganisms in the distribution system biofilms. The control of biological stability of drinking water during its transport in distribution systems is an actual challenge in terms of public health, which requests sensitive and rapid analytical tools. On line, non destructive technics for early measurement of biofilm accumulation, detection of pathogens in biofilms, and rapid evaluation of the disinfection efficiency represent the main objectives of the programme. All industrial sectors or institutions using water are concerned by the development of such technics.