Eastern Fence Lizards (Sceloporus undulatus) in middle Tennessee are commonly parasitized by chiggers (Acari: Trombiculidae), but little is known about the ecological significance of this host-parasite system. Thus, I sampled S. undulatus and their habitats monthly to determine the seasonal pattern in chigger abundance and infestation intensity. Chigger abundance was low (mean = 1.8 chiggers) in the spring (April and May), eightfold higher throughout the summer, and declined sixfold in the fall (September and October). In general, infestation intensities on S. undulatus (males, females, and juveniles) followed the same pattern except that mean infestation intensity of males declined during the summer in spite of persistently high chigger abundance. The results of this study suggest that seasonal changes in chigger abundance are a major factor influencing infestation intensities on S. undulatus.