When a positive reinforcer is scheduled contingently upon the occurrence of a behavior, that behavior is likely to increase in frequency (e.g., Skinner, 1938). Most theoretical and practical interest in positive reinforcers and in reinforcer schedules has focused on this aspect of the reinforcement process. In contrast, less attention has been addressed to the fact that a reinforcer can also engender behaviors such as general activity (Killeen, 1975), distress calling (Starr, 1978), and drinking (Falk, 1961): activities that can be established and maintained without a contingent relationship between that behavior and the scheduled reinforcer. This chapter is concerned with this latter aspect of positive reinforcement and, in particular, with the possibility that such behaviors are induced by one of two types of motivational states that persist following reinforcer termination. We describe the results of recent experiments suggesting that a positive reinforcer induces one type of state that potentiates stereotyped patterns of species-typical behavior and a second type of state that enhances exploratory-like behaviors that operate on and modify the organism's environment.