Background: Networking is an essential part of research. Several funding bodies are trying to promote networking to increase research capabilities. However, few studies to identify the key components of networking have been undertaken so far.

Objectives: To identify and to describe international networks working on epidemiology and public health issues.

Methods: An electronic search was done in Medline, Embase, The Cochrane Library, and the ISI Web of Knowledge databases. The main international societies of epidemiology and/or public health were contacted. Several funding bodies were also searched to identify any other potential networks. A survey was sent to all the identified networks and, if available, their website was scrutinized.

Results: 112 possible networks were identified. 61 networks had enough data for the analysis. One third of the analyzed networks had between 1-5 units. A 70% have central office. 57% of the networks were established in the United Kingdom (18) and the United States of America (17). 33% of the networks performed activities related to epidemiology surveillance, a 52% supported research, and 62% supported the developing of health policies. More than a third of the networks had an annual budget superior to 1 million Euro; meanwhile another third of the networks had less than 400.000 Euro of annual budget

Conclusions: It has been identified a remarkable number of networks, and we obtained information from more than half of them. Networks are quite heterogeneous. Funding was divided in extreme positions, from extremely well funded networks to poorly funded ones. Although the study has several limitations to its conclusions related to the small and incomplete response of the survey, the data available could be an excellent start point for future research in this area.