BACKGROUND: Re-organization of the English National Health Service (NHS) has fragmented the public health workforce, relocating teams from about 100 health authorities into over 300 primary care trusts (PCTs). The UK Government announced the setting up of public health networks (PHNs) as a solution to the problems created by fragmentation. METHODS: Fifty-seven semi-structured telephone interviews were held with key players in PHNs in all strategic health authority areas in England in early 2003. RESULTS: PHNs appeared to be primarily networks of public health professionals rather than of organizations. Informants were unsure about PCTs' commitment to public health. Predominantly, members were those NHS personnel with a clear and explicit public health role. Most PHNs intended to include others later (e.g. health visitors, environmental health officers), although a few thought that inclusivity was essential from the start. Continuing professional development for public health personnel dominated the work being undertaken, with some collaborative work across PCTs. PHNs were seen as a compulsory reconfiguration of existing networks, and informants doubted that they were appropriate for the many levels of networking that public health work requires. CONCLUSION: The formation of PHNs does not appear to have been either necessary or sufficient. However, the public health community has a well-established tradition of networking, and therefore has the skills to use PHNs advantageously.