This dissertation studies the spread of sports for all in Sweden during the years 1945 to 1981. The purposes of the dissertation are twofold: in part to survey the forms of physical activities which were launched as sports for all after 1945, in part to answer the question: Why have almost all voluntarily organized sports in Sweden been part of one organization since the 1970s? In order to handle the diversities of activities that can fall within the concept of sport, two principal abstractions of the concept are used: one rigorous and one flexible. Which definition one uses influences how physical activities are organized in a society. Earlier research into the history of the Swedish sports movement has concluded that it has had a relatively high degree of autonomy in relation to the state. This finding is questioned in this dissertation. Sveriges Riksidrottsförbund (RF) was the largest Swedish sports organization throughout the 20th century and at same time the organization the government relied on to develop sports policies and distribute the financial contribution from the state to the sports movement. This means that RF has played two roles, as an umbrella organization within the Swedish sports movement and as leader of the organizations within the Swedish sports movement, popular movement and semi-public authority. The dissertation shows that the two roles, that RF played, have caused conflicts of interest within the organization. That is made plain when one studies the spread of sports for all. Most members of the organization just wanted to practise different sports and were not interested in the leading organization’s desire to promote a great many different kinds of physical acitivites according to a flexible concept of sport. These members were not interested in strengthening the organization’s leading position within sports. There are not many conceptions that are so universally and uncritically accepted as the conception of the connection between physical activity and health. Sports for all came to age in a society where more and more people were told to use part of their leisure time to take part in physical activities. A societal consensus prevailed that the population’s health was on the decline due to the increased standard of living, which was creating an inactive and unhealthy population. This has meant that sports for all have been an asset of power for the sports organizations and that they have fought for authority and control over sports for all; a struggle fought over the language and thoughts as much as over sport activities. Since 1945 large campaigns to get the population to become more physically active irrespective of physical ability have been common.