Focal epileptic activity can be expected to influence distant brain areas via far reaching connections. To investigate such interactions the effects of focal epileptic activity on the metabolism of the brain were investigated in the rat cortex. Focal epileptic activity was induced by the application of penicillin onto the motor cortex. The focus, and to a lesser extent homotopic contralateral brain areas, showed an increase in the regional cerebral metabolic rate of glucose (rCMRGIc) as measured by [14C]deoxyglucose autoradiography. This focal hypermetabolism was accompanied by widespread hypometabolism lateral to the focus. The decrease of rCMRGIc occurred in somatosensory cortical areas but not in the motor cortex behind or in front of the focus, the perirhinal cortex or the occipital cortex. It was associated with an increase in metabolic rate in the ventrolateral, ventroposteromedial, ventroposterolateral and, in particular, posterior nuclei of the thalamus. It is hypothesized that the widespread reduction of rCMRGIc in the somatosensory cortical areas is due to inhibition via thalamic nuclei caused by activity in the motor cortex.