Classical conditioning theories have long played a role in models and treatment of anxiety disorders, but important questions remain. One significant issue is the nature of aversive responses elicited by aversively conditioned stimuli. We argue that the conditioning of discrete cues models fear, and the conditioning of contextual stimuli and long-duration cues models anxiety. One aim of this proposal is to characterize the psychophysiological, emotional, and biological concomitants of these different types of conditioning. Another aim is to examine the impact of prior stress on conditioned fear responses. Stress affects limbic regions that are implicated in learning and memory, as well as mood and anxiety disorders, suggesting that stress impairs limbic-mediated components of associative learning. We hypothesize that stress will have little impact on implicit motor learning, but will affect associative learning that is dependent on the hippocampus. We will explore the effect of stress on acquisition and retention of different types of motor (cerebellum-dependent), emotional (amygdala-dependent), and cognitive (hippocampus-dependent) associative processes.