Aim To assess ambulatory activity of children with cerebral palsy (CP), aged 7 to 13 years, and identify associated characteristics. Method Sixty-two children with spastic CP (39 males, 23 females; mean age 10y 1mo, SD 1y 8mo; age range 7-13y), classified as Gross Motor Function Classification System (GMFCS) levels I to III, participated. Ambulatory activity was measured during 1 week with a StepWatch activity monitor as steps per day, and time spent at medium and high step rates. Multiple linear regression analyses were performed following a backward selection procedure until only independent variables with p<0.05 remained in the model. Ambulatory activity outcome parameters served as dependent variables, and disease, personal, and environmental characteristics as independent variables. Ambulatory activity was corrected for body height. Results Children took more steps during school days (5169 steps, SD 1641) than during weekend days (4158 steps, SD 2048; p<0.001). Higher GMFCS level, bilateral CP, and higher age were associated with lower ambulatory activity on school days (R(2) ranged from 43-53%), whereas bilateral CP, higher age, and no sport club participation were associated with lower ambulatory activity in the weekend (R(2) ranged from 21-42%). Correcting for body height decreased the association with age. Interpretation Interventions should focus at increasing physical activity at the weekend for children with bilateral spastic CP. CI - (c) The Authors. Developmental Medicine & Child Neurology (c) 2012 Mac Keith Press.