In the context of influenza pandemic preparedness planning, a surveillance system for influenza and other acute respiratory illnesses was implemented in Lower Saxony at the beginning of the influenza season 2004/2005 and coordinated by the Governmental Institute of Public Health of Lower Saxony. This surveillance system represents an addition to already existing national monitoring systems. The goal of this surveillance system is to have available prompt information on the beginning, course and end of the influenza season and to recognise the spectrum of pathogens and identify outbreaks of other viral acute respiratory illnesses (ARI). For this purpose an all-season surveillance was established consisting of two supplementary modules. The first module is a symptom-oriented surveillance of acute respiratory illnesses in children of pre-school day care facilities. In the second module a virological surveillance in co-operation with selected medical practices was established. While the temporal course and burden of ARI in all Lower Saxony can be assessed by the surveillance of children in the day-care facilities in a sensitive, but less specific way, the virological surveillance provides highly specific information on the prevailing pathogens in ARI patients at a certain time. This information, in return, gives an indication about the responsible pathogens causing ARI in children of the day-care facilities. The first experience with these two complementary surveillance modules shows that in Lower Saxony a well accepted, prompt and meaningful monitoring system is available for the recognition and description of the occurrence of ARI and concomitantly of influenza. An extension of this surveillance to other pathogens or disease scenarios is possible.