Although effects of temperature on sprint performances of lizards are well documented, influences of slope are much less well known, and few studies have examined comparable effects on stamina. We monitored locomotor performance of Eastern Fence Lizards, Sceloporus undulatus, at temperatures from 15–40°C and slopes from 0–45° using two types of nonmotorized tracks. Body size did not significantly affect performance, but both sprint performance and stamina were significantly affected by temperature and slope. The optimal temperature for performance is approximately 30°C. As slope increased, both sprint speed and stamina progressively decreased. Mean incline speeds were significantly greater than mean decline speeds at all slopes other than 0°. There was a direct relationship between sprinting ability and stamina; lizards that ran faster tended to run for longer periods of time and distances. Neither sprint speed nor stamina data support the hypothesis that running velocity of lizards is limited by mechanical power output.