This study compared two ankle-mounted pedometers [StepWatch 3 (SW-3(Ankle)) and Activity Monitoring Pod 331 (AMP(Ankle))] and two waist-mounted pedometers [New Lifestyles NL-2000 (NL(Waist)) and Digiwalker SW-701 (SW-701(Waist))] under controlled and free-living conditions. In part I, 20 participants walked on a treadmill at speeds of 27-107 m min(-1). Actual steps were counted with a hand counter. In part II, participants performed leg swinging, heel tapping, stationary cycling, and car driving. In part III, 15 participants wore all pedometers for a 24 h period. The SW-3(Ankle) displayed values that were within 1% of actual steps during treadmill walking at all speeds. The other devices underestimated steps at slow speeds but all gave mean values that were within +/-3% of actual steps at 80 m min(-1) and above. The SW-3(Ankle) registered some steps during heel tapping, leg swinging, and cycling, while the AMP(Ankle) was only responsive to leg swinging. During car driving no devices recorded more than eight steps, on average. Over 24 h, the AMP(Ankle) recorded 18% fewer steps than the SW-3(Ankle) (P<0.05), while the SW-701(Waist) and the NL(Waist) recorded 15 and 11% less than the SW-3(Ankle), respectively (NSD). The SW-3(Ankle) has superior accuracy at slow treadmill walking speeds (although it was also more likely to detect "fidgeting" activities). Over 24 h, the SW-3(Ankle) tended to give higher estimates of steps per day than the other ankle- and waist-mounted pedometers.