Prenatal benzodiazepine exposure is associated with behavioral and neurochemical alterations in the early postnatal period. To determine the persistence of these effects, we evaluated pentylenetetrazole-induced seizure threshold and GABA-dependent chloride uptake in mice at 6 and 12 months of age after prenatal lorazepam exposure. Seizure threshhold was reduced after acute lorazepam pretreatment in mice exposed to lorazepam prenatally, compared to control groups, at 6 and 12 months of age. Maximal GABA-dependent chloride uptake was also reduced in exposed mice at 6 and 12 months of age. These data indicate that behavioral and neurochemical alterations persist well into maturity after prenatal lorazepam exposure.