Little information is available regarding the relative effectiveness of various treadmill exercise protocols in eliciting maximal oxygen consumption (VO2 max) values in children. In this study of 10- to 12-year-old boys, running protocols produced significantly higher VO2 max levels compared with walking, but there were no important differences in continuous, intermittent, and handrail-supported running schedules. The intermittent run protocols, however, prolonged the test duration. Studies examining VO2 max in children should utilize standard criteria for demonstrating peak oxygen intake. In this study criteria of VO2 plateau, peak heart rate over 198 and respiratory quotient exceeding 1.0 were satisfied most commonly with running protocols.