The influence of a chronic phenobarbital (PhB) treatment on postnatal evolution of local cerebral metabolic rates for glucose (LCMRglc) was studied in 58 cerebral structures of freely moving rats. The animals received a daily subcutaneous injection of PhB at a dose of 50 mg/kg between days 2 and 35 or an equivalent volume of saline for controls and were studied at 5 postnatal stages, i.e. 10, 14, 17, 21 and 35 days, and at the adult stage. Body and brain weights were both reduced by 6-21% over the whole period studied. PhB exposure induced significant decreases in LCMRglc during the period of pharmacological treatment, i.e. until 35 days, except at the stage of 17 days as well as long-term reductions in LCMRglc of adult rats in 36 out of the 58 brain regions studied. These decreases affected all systems studied, sensory systems as well as limbic, hypothalamic, motor and white matter areas. In addition to a growth retardation, PhB also seemed to be able to induce a delay in the acquisition of auditory function which matures early during postnatal life. The long-term deficits in cerebral energy metabolism due to PhB in the adult rat also confirm the behavioral deficits which have been shown previously after early PhB exposure.