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The conditions that permitted the oral self-administration of a drug solution to develop as a reinforcing event for rats, so that a drug solution was preferred to a concurrently available vehicle (water), were elucidated. The genesis of a preference for a solution depended importantly on a history wherein the discriminative stimulus (a light SD) present in proximity to the drug-solution location had been associated with the self-administration of an ethanol solution. Once the SD was established, it stably determined fluid choice even if that fluid was a second source of water. The results indicate that the sources of persistence and malleability of drug abuse behavior may lie in the instigating properties of established discriminative stimuli.