OBJECTIVE To objectively measure levels of physical activity in children, following treatment for acute lymphoblastic leukaemia (ALL). METHODS Nineteen children who had completed treatment for ALL 6 months-5 years prior to study enrollment wore an accelerometer for 2 weekdays and 2 weekend days. RESULTS The children spent an average of 141 +/- 74 min/day engaged in moderate to vigorous physical activity (MVPA), an amount similar to that previously documented in healthy children. Only three of the 19 subjects averaged less MVPA than the recommended amount (at least 60 min/day). MVPA levels were significantly higher on weekdays than weekend days (P= 0.006). Overall, boys engaged in significantly more MVPA than girls (P= 0.029). MVPA time was negatively correlated with age (r =-0.80) and age at diagnosis (r =-0.87). No trend between MVPA and time off treatment or body mass index was identified. CONCLUSIONS Survivors of childhood ALL appear to be engaging in similar amounts of MVPA as those of the healthy children and are meeting recommended levels of physical activity.