Real-time surveillance information is the prerequisite for accurate influenza diagnosis followed by appropriate treatment of acute influenza with neuraminidase inhibitors. With REALFLU trade mark Surveillance, Hoffmann-La Roche has developed an international early warning system for influenza. The feasibility of the newly developed real-time influenza surveillance in Germany was tested and the results were compared with those of the established German influenza sentinel system of Influenza Study Group (Arbeitsgemeinschaft Influenza, AGI). The evaluation of the REALFLU trade mark Surveillance was performed during the winters of 1999/2000 and 2000/2001. The percentage of influenza-like illnesses among patients seen by the reporting physicians and positives of the Roche Influenza A/B Rapid Test were reported daily by internet, evaluated and could be called up on dynamic internet web pages real-time. The group of project participants could at any time call up the evaluations of the current data on password-protected internet web pages. A retrospective comparison with data obtained by the AGI showed good agreement between the two systems. Even better agreement was obtained on comparing the data with the virus isolates of the National Reference Centers (NRZ). This confirms the reliability of the selected methodology. REALFLU trade mark Surveillance provided information about influenza outbreaks 1-2 weeks earlier than NRZ and the AGI. The results show that it is possible and reasonable to conduct influenza surveillance on a real-time basis. In an overall context of REALFLU trade mark Surveillance, the German pilot project was capable of reflecting the influenza situation on a real-time and regionalized basis during both winters. The Roche Influenza A/B Rapid test proved to be a useful surveillance tool.