Using high-resolution single photon emission computed tomography, the authors studied changes in cerebral blood flow (CBF) in six healthy men after the men rapidly consumed intoxicating amounts of ethanol. When the subjects were given intravenous placebo before ethanol intake, regional CBF was significantly increased over baseline in the right prefrontal cortex, but no significant change in CBF was observed when the subjects received intravenous naloxone before ethanol intake. The results indicate that euphoria occurring during acute ethanol intake is associated with activation of the right prefrontal cortex and mediated through the endogenous opioid system.