During postnatal development, young laboratory rats, Rattus norvegicus, exhibit a variety of locomotor-rotational movements, that is, runs and jerk-jumps, in both playful and nonplayful contexts. The frequency of movement types differed between contexts. Some contexts, such as exploration and sleeping, contained spontaneously (i.e., possible eliciting stimuli were not observed) occurring jerk-jumps which varied with increasing age. In some contexts, such as social play, in which locomotor-rotational movements were elicited by observed stimuli, the frequency of jerk-jumps remained similar throughout ontogeny. During social play some locomotor-rotational movements were found to have immediate functions, such as achieving advantage over the partner during play-fighting, and as a means of terminating sensory input from the partner at the end of social contact.