The purpose of this study was to examine the effects of walking speed on the accuracy of measurement of steps, distance, and energy expenditure of two commercially available Omron pedometers [HJ-720IT-E2 (HJ-720) and HJ-113-E (HJ-113)]. Twenty-four untrained males (age, 22.7 ± 2.8 years; BMI, 24.38 ± 2.19 kg m(-2); body fat (%), 16 ± 2.2; VO(2max), 40.2 ± 6.5 ml kg(-1) min(-1)) and 18 females (age, 22.4 ± 2.9 years; BMI, 21.68 ± 2.43 kg m(-2); body fat (%), 23% ± 1.8; VO(2max), 35.9 ± 2.8 ml kg(-1) min(-1)) walked at five different velocities (54, 67, 80, 94 and 107 m min(-1)) on a treadmill in 5-min stages while wearing three types of pedometers: (a) HJ-720, (b) HJ-113, and (c) Yamax Digi-Walker SW-200 (YAM). Step-count for each pedometer was recorded at the end of each stage and compared with the value of a hand counter. Additionally, Omron pedometers were evaluated on their distance and energy expenditure (against VO(2) measurement with a gas-exchange analyzer) accuracy during each stage. HJ-720 and HJ-113 demonstrated high accuracy (r = 0.80-0.99) at all speeds. YAM underestimated step-count only at 54 m min(-1) (r = 0.46). HJ-720 and HJ-113 overestimated distance at slower speeds and underestimated distance at faster speeds, providing mean distance values that where to within 1.5-4% at 80 m min(-1). HJ-720 and HJ-113 underestimated energy expenditure (gross kilocalories) by 28%, when compared to indirect calorimetry. These results suggest that although the Omron HJ-720 and HJ-113 pedometers are accurate in the measurement of step-count, they demonstrate limited accuracy in the assessment of traveled distance and energy expenditure in a speed-dependent manner.