A public health network involves several and different health professionals who work in synergy to achieve a common objective: to improve the management of a given disease. Per se, this objective could not be achieved by each of these professionals if working separately. In practice, existing public health networks ensue from very different legal frameworks and come up against various impediments. They have been developed mainly for the management of chronic and serious diseases (e.g. asthma, diabetes, virus C hepatitis, Parkinson's disease, drug abuse). Public health networks can be a very valuable source of data for clinical and epidemiological research, mainly because patients are followed up over a very long period and information coming from various health professionals (general practitioners, specialists, nurses, etc.) is centralized and recorded in a common database. It can also be useful for pharmacovigilance purposes (assessment of Type A and delayed reactions). In any case, the relative interest of such networks should be regularly assessed by an ad hoc methodology, e.g. an experimental or pseudo-experimental design vs. a reference. Despite the fact that there are relatively few operational networks, they can be of great interest for clinical research.