Recent developments of multichannel SQUID magnetometer systems enabled us to perform magnetoencephalography (MEG) as a means of non-invasive functional brain mapping in patients. In this review, clinical applications of somatosensory, auditory and visual evoked magnetic fields are described. For the source estimation, current dipole models were used in a sphere approximated from the head shape of each subject as determined by MRI. Localization errors of sources in the multimodal evoked responses were evaluated as low as 2 to 3mm when related to cerebral structures. Further developments of clinical MEG systems are discussed.