Recall of physical activity is a known problem affecting all forms of self-report. Participants age 8–16 years contributed to 16 focus groups and 24 interviews based on cognitive interviewing (n = 8) and think-aloud (n = 8) and general probing (n = 8) techniques. When unassisted, participants readily described physical activity mode but gave vague descriptions of daily activities. In contrast, the close detail of frequency, intensity, and duration of these activities was only more fully developed through prompting. Talk-based methods can provide considerable insight into developing more reliable and valid physical activity self-reports.