The purpose of this study was to compare the energy expenditure during. positive and negative grade running. This comparison ,.,as expressed as a ratio utilizing net percent difference from the horizontal for both downgrade andupgrade values (m1/kg-min). A group of ten highly conditioned runners was tested on three separate treadmill runs utilizing a +6% grade, 0% grade, and a –6% grade. All runs were of a seven minute duration at an average speed of 200 m/min. Variables measured were heart rate, oxygen consumption, leg length, stride length, and step frequency. It was found that the fractional utilization of the aerobic capacity varied from44% (-6% grade) to 78% (+6% grade). Energy requirements increased 40% (+6% grade) and decreased 27% (-6% grade) from horizontal values. The resultant positive:negative work ratio was 1.92:1. Correlations among -variables fluctuated from slight to moderate with the most significant being a high positive correlation between energy expenditure and step frequency.