It is important to get a better understanding of the relationship between sport participation on the one hand and health and health care costs on the other. For that purpose, the research in this thesis shows that sport participation is positively associated to significantly lower risks of morbidity, type 2 diabetes, prediabetes and obesity. However, the relationship between sport participation and health differs between groups. For several health outcomes, the positive effects of sport participation are significantly greater for people with a healthy weight than for obese persons. Another finding is that socioeconomic inequalities in sports participation (with the most vulnerable groups participating the least) seem contribute considerably, and much more than physical activity, to the socioeconomic inequalities in health outcomes. The research also shows that there exists a strong socioeconomic gradient in health care costs in the Netherlands: controlling for the population structure, poor neighborhoods have substantially higher costs than affluent neighborhoods. In addition, neighborhoods with a higher percentage of voluntary sports club members have significantly lower average health care costs. This relationship seems to be independent of the socioeconomic level of a neighborhood. Finally, the research shows that the socioeconomic inequalities in physical activity behavior have increased significantly in the Netherlands due to the Covid-19 pandemic and the measures to prevent the spread of the virus. In conclusion, the research in this thesis demonstrates that sports participation can be an important preventive medicine for improving health, reducing socioeconomic health inequalities, as well as lowering health care costs.