Foraging theories evaluate how animals make choices in prey. Some important factors in prey selection are size of prey and distance to pursuit, which can be affected by prey availability, ease of capture, and the time for chasing, handling, and ingesting prey. We examined prey size selection in an ambush (sit-and-wait) predator, the Eastern Fence Lizard, Sceloporus undulatus, in Maryland and Delaware, USA. We tested whether animals selected prey by size by presenting two sizes of prey (crickets) in a choice test in the field and measured latency to attack prey through a series of presentations of mealworm prey at different distances, recording the distance and time to attack. Adult males preferred larger prey and female juveniles preferred smaller prey. Distances to pursue prey did not differ between sexes but males had a longer attack latency than did females. Mean sprint speed on a vertical surface correlated with maximum burst speed, body mass, and body condition; males were more likely to run than were females, particularly during the spring. We found that our ambush foragers show prey size preferences and demonstrate a distance beyond which they will pursue prey. Because prey size preferences were not predicted by body size alone and cut-off distances did not vary seasonally, factors affecting foraging behavior warrant further attention.