We investigated the localization of current sources in the time and frequency domain from spontaneous MEG data recorded from nine epileptic patients (six females; three males) randomly selected, who had a mean age of 41 years old (range of 17-78 years old), with different types of epilepsy. The MEG data were recorded in a magnetically shielded room with a whole-head 122 channel biomagnetometer. For each MEG spike, we calculated the single Equivalent Current Dipole (ECD) sources at the initial spike peaks with a spherical model. MRI and EEG findings were available in patients' records. Prominent low frequencies can be seen in the majority of channels. For each patient there was an increase of the frequency range after the ECD in comparison with the frequency range before the ECD, in the whole study group due to epileptic discharge which is statistically significant (p=0.02). There was also a statistical significant difference in the increase of the frequency range in four patients with pathologic MRI (p=0.05), in five patients with normal MRI (p=0.02), in five patients with a high incidence of seizures (p=0.04) and in four patients with onset<10 years (p=0.04). The MEG analysis of neuromagnetic data gives information about the modification of the frequency range in the epileptic brains.