Age profiling of fossil faunal samples relies on the correlation of animal tooth-wear patterns with life history stages, but the criteria used to infer these stages are not necessarily valid. Here we redefine some commonly used prey age classes, such as “juvenile,” “prime-age adult,” and “old adult,” based on the variable characteristics of tooth wear that we have observed in different ungulate size classes, and argue that prey vulnerability to predation is not so clearly predicted by the simplified age classes in widespread use by zooarchaeologists. We recommend instead classifying the youngest animal remains as either young juvenile or subadult juvenile, and adult remains as early prime, late prime or old, and provide specific criteria of dental eruption and occlusal wear for making these determinations. We argue this refined age profiling system, when used in combination with other types of zooarchaeological and taphonomic data, can provide accurate inferences of faunal accumulation processes.