Cortical stimulation (CS) is important in planning epilepsy surgery in both adults and children. The goal of epilepsy surgery is seizure control without a significant neurologic deficit. The term eloquent cortex refers to cortical areas subserving the critical neurologic functions of motor, somatosensory, language, and memory. The identification of these areas is called cortical or functional mapping. CS may either activate or inhibit neurologic function from the stimulated area, thus identifying its function. CS also produces epileptiform activity, either spikes or sharp waves, called afterdischarges (ADs). The stimulation intensity that results in an AD is called the AD threshold. The techniques and precautions of CS are reviewed, including background electronic principles, stimulation parameters, and recording and testing methods, emphasizing its application to children. The immature cortex is more resistant to CS, which depends on the degree of myelination. Because more energy is needed to elicit a functional response in children, different stimulation parameters are used, especially a longer pulse duration. In addition, functional mapping in adults is generally performed at stimulation intensities below the AD threshold, whereas in younger children, functional responses may occur only above the AD threshold.