SUMMARYAdult C57BL/lOBg mice, normally resistant to audiogenic seizures, became susceptible when the mothers drank 10%ethanol in water during pregnancy and for 14 days postpartem. Reserpine enhanced the incidence of seiqres, and the effect was reversed by 5‐hydrOxYtryp tophan but not by dihydroxyphenylalanine p‐Chlorophenylalanine also enhanced the inci dence of seizures, whereas a‐methyl‐p‐tyrosine did not effect. Monosodium glutamate almost completely prevented seizures. These results are consistent with the interpretation that the serotonergic systems may be among those involved in the seizure mechanism induced by fetal and early exposure t