The acute and extended effects of ethanol ingestion were examined in five alcoholic subjects, and five "social" drinkers. Six physiological and four subjective report measures were taken before, during and up to 90 min after the ingestion of ethanol in three doses and placebo. Findings showed that alcohol exerted significant dose-related physiological effects in the initial minutes of ingestion, and in extended analyses of physiological and subjective measures in both groups of drinkers. Alcoholics and social drinkers generally did not differ in their physiological responses to alcohol doses and placebo, while some evidence for tolerance to reported euphoric effects of alcohol in the alcoholic subjects was found. The possibility is raised that early physiological responses observed during ethanol ingestion may arise not only from pharmacological effects of the drink, but may also be evidence for conditional predrink responses.