One of the missions of the Air and Health Surveillance Program (PSAS-9) of the French Institute for Public Health Surveillance (InVS) is to develop and update exposure-risk models in the field of urban air pollution and health, in order to enable public health professionals to conduct health impact assessments at the local and national levels. The development of these functions for long-term risk therefore naturally falls within the scope of this program’s activities. Accordingly, with a view to such a project, an initial framework document has been drafted. The objective of this document, after presenting all cohort studies published to date on the long-term effects of urban air pollution on mortality, is to define the criteria for selecting or defining the “ideal” cohort that will best allow for estimating the long-term effects of chronic exposure to urban air pollution.