Objectives: The aim of this study was to identify the most prevalent reported activities performed by Australian children during the lunchtime and after school periods; and estimate the mean duration of a typical bout of the most prevalent activities performed during the lunchtime and after school periods. Design: This study was a secondary data analysis of the 2007 Australian National Children's Nutrition and Physical Activity Survey. Method: Use of time data were collected from Australian children aged 10.0-13.9 years (n=794) using the Multimedia Activity Recall for Children and Adults (MARCA). The most prevalent self-reported activities for the lunchtime and after school period on school days were determined by mean duration across the sample. The estimated energy cost for each of the activities was reported based on the Compendium of Energy Expenditures for Youth. Results: A list of the 20 most prevalent lunchtime activities and 30 most prevalent after school activities is presented. Of the most prevalent lunchtime activities, 35% were classified as sedentary and 65% as moderate to vigorous physical activities. During the after school period, 57% of the most prevalent activities were classified as sedentary and only 43% as moderate to vigorous physical activities. Conclusions: These data may assist in the development or refinement of activity checklists with greater content validity, which may be used in combination with objective measures to provide important contextual information about the types of activities being performed and inform the development of appropriately targeted interventions.