A concurrent recording of electroencephalography (EEG), magnetoencephalography (MEG) and electromyography (EMG) was carried out in a patient with epilepsia partialis continua. He had continuous clonic jerks in his right hand and fingers. The EMG electrodes were placed on the thumb of his right hand. We observed numerous MEG spikes in the left central region and about half of them were accompanied by EMG potentials with a latency of about 20 msec. The EEG spikes appeared less frequently, had low amplitudes, and had unclear morphologies and further, no clear association with EMG potentials. MEG spikes were more reliably associated with individual jerks, exemplified by EMG potentials, than the EEG spikes. The MEG spikes were sharper than EEG spikes and were about 20 msec wide. The intracranial dipole localization of the MEG spikes was estimated by overlaying the calculated generator sites on magnetic resonance images. It was found that the spikes converged along a line, presumably the central sulcus. The practical benefits of the MEG as a diagnostic tool in epilepsy are illustrated.