The aim was to gain knowledge of young people's physical status and physical activity, and to further the understanding of the role of school physical education in a salutogenic public health perspective. Two studies were performed in southern Sweden. Study 1 was performed in 1996 among 301 adolescents aged 16-19 in upper secondary school. It comprised three parts: a questionnaire, seven physical tests, anthropometrical measures and information on every student's grades. Study 2, with a longitudinal design and annual measurements, was performed in 2000-2003 (n=205- 275) among children aged 6-12 in two primary schools, one intervention school with expanded physical education lessons, and one norm school which followed the stipulated curricular time. The study comprised a questionnaire, eleven physical tests and anthropometrical measures. In Study 1, students in practical education for occupations such as industrial and building workers, mechanics, assistant nurses and hairdressers, all of which are occupations involving physical effort, had lower physical capacity than students in theoretical education among both boys and girls. A correlation was found between physical capacity and grades. An interrelation between Sense of Coherence (SOC) and attitudes to physical education was found, indicating that past experiences of physical activity and physical education could contribute to the development of SOC, and actual levels of SOC could influence the persistent attitudes to physical education and be important for lifelong physical activity. Study 2 showed high self perceived competence in physical education among children to be associated with high physical performance, male gender, low age, living with both parents, high self perceived physical fitness and enjoying physical education. Children who followed an expanded physical education programme during the three-year follow up showed positive changes in physical performance compared to children in the norm school. The number of children with increasing body mass index (BMI) rose in both schools, but a lower increase in BMI could be seen in the intervention school. In both Study 1 and 2, the highest physical capacity was found among children and adolescents who reported a high level of physical activity in leisure time. This thesis shows it is possible to achieve improvement in physical status among young people with an increase of physical education lessons in school. Differences in physical capacity between prospective blue-collar and white-collar workers already in adolescence during education emphasize the need for early interventions to increase physical activity and capacity in young people. Physical education in the school setting could be seen as an important arena for improving physical capacity, positive self-perceptions and positive attitudes to physical activity, which could be important for public health.