Whole-scalp MEG has proved to be a suitable tool for preoperative evaluation of patients suffering from drug-resistant focal epilepsy. MEG recordings are non-invasive and safe for the subject, and no demanding preparations of the patient are needed before measurement. The MEG recordings may reveal several epileptic foci, and the order of activation can be resolved in millisecond scale. In addition, epileptic cortex can be localized with respect to important functional areas, such as sensorimotor or visual cortices, and these areas can be visualized in a same brain reconstruction. This helps in patient selection and planning of the operation. Moreover, prior MEG localization of epileptic foci and functionally important areas aids in placing the intracranial electrodes to right places, when needed.