Background. In many European countries, primary care surveillance networks play a role in public health surveillance. Objectives. To update an inventory of surveillance networks, to describe them and to report on their organization and function in a standardized way. To investigate whether and under what conditions their information can contribute to surveillance at a European level. Methods. Surveillance networks were defined as 'A network of practices or community based primary care physicians who monitor one or more specific illness problems on a regular and continuing basis'. For the inventory questionnaires were sent out, followed by site visits to seven networks using a standardized audit checklist. Results. We sent out 75 questionnaires and received 57 back (73% response rate), with 33 (58% of responders) fitting our selection criteria. National surveillance networks were identified in 11 countries. Many had an infectious disease surveillance component, particularly for influenza. Most were funded by the Ministry of Health, some by research funds. The median number of general practitioners was 120, comprising a stable group of general practitioners and covering a representative sample of the general population. The frequency of reporting varied from daily to annually, depending on the purpose of the network. Conclusions. A large number of primary care surveillance networks exist in Europe. Their value has been shown with the surveillance of influenza, but the challenge is now to extend their use to other diseases. When fulfilling identical minimal criteria they can provide comparable estimates of morbidity, ultimately leading to improved national and European surveillance.