Medical demographics has become a major public health issue. An understanding of the subject is essential for striking a proper balance between the number of practitioners and the needs of the population. This project has three components: 1. Population projections made in 1990, and updated in 1999 using a demo-economic model developed at INED, anticipated a 30% decrease in anaesthesiologist numbers by the year 2020. Based on this finding, a national survey of anaesthesiologists was conducted by INED in conjunction with the two French professional bodies of anaesthesiologists, the CFAR and the SFAR, in order to gain a better understanding of the key demographic and organizational characteristics of this medical specialty. This survey was based on a self-administered questionnaire. Because of the inaccuracy of the national data, the survey's initial aim was to count the physicians, and then to describe the profession and its population dynamics. The unique methods used in this survey (census, adjustment techniques and model for estimating numbers of practitioners based on numbers of posts) can also be used for population analysis in other specialties. 2. Assistance Publique - Hôpitaux de Paris (AP- HP) employs 48% of these specialists in the Ile-de-France region and trains all the region's physicians. However, while the numerus clausus increased sharply in 2008, this should not have a significant effect on the anticipated drop in the number of specialists (a 20% decrease by 2020) because of the demographic inertia engendered by the length of time required for medical students to complete their studies. A demographic study of the 12,000 AP-HP doctors was carried out as part of the AP-HP's strategic plan for 2005-2009. The study aimed to inform the institution's demographic and organizational strategy for handling this decrease and so improve management of its various healthcare missions. This study was updated under the AP-HP's new strategic plan for 2010-2014. 3. Updating national and regional projections for medical disciplines at demographic risk, based on data provided by the Conseil National de l'Ordre des Médecins, the CFAR-SFAR-INED survey and AP-HP data, and estimating training needs.