Physical activity is associated with better health. Two sources of activity for children are walking to school and taking part in organized sports. This study examined factors associated with participation in these activities. The study followed 17,561 singleton children recruited during 2000-2002 in the UK. All participants were interviewed in their own homes at 9 months, 3 years and 5 years' follow-up to track engagement in walking to school or organized sports; all measures were self-reports. Children were less likely to walk to school as income and parental education increased. However, if the parent plays with the child in high income families the child is more likely to walk to school. Children taking part in organized activities were from higher income, higher education families, with a car, in a "good" area with non-working mothers. However, in low socioeconomic families where the parent plays with the child the child is more libel" +n +9Iro harl- in nroani-rarl nru-iac