Three physical activity questionnaires were validated against heart rate (HR) monitoring and motion accelerometer data. All three methods were carried out simultaneously on 62 children ages 4-8 years on 4 consecutive days. The questionnaires were filled in by the children's parents and teachers. The reported time of physical activity with moderate to vigorous intensity, expected to increase HR above 140 beats per minute (bpm), correlated with the time of HR > or = 140 bpm and > or = 150 bpm (r = .40, p < .01) and with the accelerometer score (r = .53, p < .0001). Correlation between the HR > or = 140 bpm and accelerometer score was r = .45, p < .001, and between the HR > or = 150 bpm and accelerometer score, it was r = .41, p < .01.