In rats which had received an intoxicating dose of ethanol, the concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the brain were not different from concentrations in brains of normal rats. The turnover of cerebral 5-HT, determined from rates of increase in concentration of 5-HT or of decrease in concentration of 5-HIAA after the administration of a monoamine oxidase inhibiter, was modestly decreased during ethanol intoxication.