Play fighting is a commonly reported form of play in the young of many mammals. Most of the studies on the neurobehavioral mechanisms regulating this behavior have focused on the laboratory rat. The rationale for doing so has been primarily on practical grounds. This paper seeks to answer the question. "How good is the rat as a model of mammalian play fighting?" A review of the detailed structure of play fighting in rats and other mammals reveals that play fighting is not a unitary activity, but rather has distinct components with each having distinct regulatory mechanisms. The rat is typical of many other mammals for some features of play fighting, but not others. Therefore, two conclusions are drawn from this review. First, given that play fighting is a composite category of behavior, questions regarding its underlying neurobehavioral mechanisms need to be narrowly constructed, so as to deal with highly specific mechanisms. For example, what mechanism regulates the pubertal decline in play fighting? Second, the rat is shown to be a good model species for the study of some features of play fighting, but it cannot be assumed to represent an "average" mammal for all features.