The techniques of magnetoencephalography (MEG) have advanced considerably recently with several major installations now being built or planned. In this paper, the present status of MEG within clinical medicine is evaluated and compared with that of other large diagnostic instruments. Deficiencies in present instruments and procedures are discussed. It is argued that in the future methods must be found of investigating sub-cortical structures which are relevant in the majority of clinically significant conditions. Some important possible lines of enquiry are indicated.