--- - |2 The capacity of 3D cameras to measure many different aspects of behavior (e.g., velocity, pattern, and posture) could contribute to the understanding of behavior. The present article describes a system for the real‐time tracking of operant behavior, which is applicable to other domains of behavioral science as well. Methods for real‐time 3D tracking of animal behavior are described, along with sample C++ programs. A demonstration using one zebrafish as a subject indicated that the present system successfully tracked the 3D motion of the fish. Moreover, the acquisition of a target response (i.e., approach to a corner of the aquarium) was demonstrated with the arrangement of a reinforcement contingency at the corner in the absence of a traditional, salient operandum. The system offers the capacity to characterize more completely ongoing behavior in learning tasks across a range of species than simply performance of discrete operant responses. The system also is capable of tracking multiple individuals simultaneously so it is possible both to study social interactions and arrange contingencies for engaging in social behavior. Other possible applications of 3D cameras are discussed. - Journal of the Experimental Analysis of Behavior, EarlyView.