A 12-year-old girl developed simple partial motor and sensory seizures due to a right perirolandic astrocytoma. Subdural EEG recording and functional stimulation disclosed close correlation between EEG-clinical manifestations of focal seizures and functional responses to cortical stimulation. This case supports the idea that responses in the perirolandic area to endogenous epileptogenic activity and to cortical stimulation reflect common underlying physiologic mechanisms.