In 1999 the National Council on Nutrition and Physical Activity in Norway appointed a committee to look into the relationship between health and physical activity, and to provide some guidelines to various populations regarding physical activity. The committee, which consisted of Sigmund B. Str?mme, Sigmund A. Anderssen, Ingvar Hjermann, Jorunn Sundgot-Borgen, Sigbj?rn Smeland, Sverre Maehlum, and Anita Andaas Aadland, produced a comprehensive 84-page report (rapport nr. 2/2000) on physical activity and health based on the currently available scientific evidence. An extract from the first part of the report, which concentrates on the significance of physical activity for various population groups follows below.