In this study, we have evaluated the physical characteristics of neonate, female, and male Mongolian racerunners (Eremias argus) and determined the age structure of a population of the species in a field located in Taean-gun, Chungnam, South Korea. The physical parameters of females and males, including snout-vent length (SVL), head length, head width, and body mass were found to be significantly interrelated. Male Mongolian racerunners exhibited significantly longer heads than the females, but other physical parameters, such as SVL, head width, and body mass did not differ between the female and male specimens. In the study population, the females ranged in age from two to eleven years old and the males ranged between two to eight years of age. The number of females and males, when separated into different age classes, did not differ within each age class. Male Mongolian racerunners evidenced greater SVL growth coefficients than the females, but asymptotic SVL did not differ between the females and males.