Associative learning can occur as a result of the arrangement of contingencies between stimuli and outcomes. The experimenter controls the occurrence of these events in classical conditioning (Pavlov, 1927) 131 . In instrumental conditioning, the experimenter arranges the environment in such a way that a response is required for a particular outcome to occur (Skinner, 1938) 153 . There may be other procedures that produce associative learning, and there are certainly other forms of learning, including habituation, various forms of perceptual learning (e.g., released image recognition learning; Suboski and Bartashunas, 1984 166 ), verbal learning, and the learning of complex motor sequences. The present chapter focuses on methods for determining the effects of drugs on associative learning with particular reference to instrumental conditioning. Classical conditioning also will be covered briefly, but no discussion of these other forms of learning will be included. This should not be taken as a reflection on the relative importance of various forms of learning.