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Over the past decade, data collected in our laboratory have demonstrated that self-administered cocaine produces Opponent-Process-like behavioral effects. Animals running a straight alley once each day for IV cocaine develop over trials an approach–avoidance conflict about re-entering the goal box. This conflict behavior is characterized by a stop in forward locomotion (usually at the very mouth of the goal box) followed by a turn and ‘retreat’ back toward the goal box. The results of a series of studies conducted over the past decade collectively suggest that the behavioral ambivalence exemplified by rats running the alley for IV cocaine stems from concurrent and opponent positive (rewarding) and negative (anxiogenic) properties of the drug—both of which are associated with the goal box. These opponent properties of cocaine have been shown to result from temporally distinct affective states. Using a …