Fifty-two patients were examined both with computed tomography using a different third generation scanner and by magnetic resonance imaging (MRI) at half Tesla field strength (Philips Gyroscan 5 S). Excellent contrast and spatial resolution as well as initial comparative results of normal anatomy and also selected clinical cases were demonstrated with the spin-echo (SE) and/or inversion recovery (IR) technique. The clinical material included a residual prolactinoma after transphenoidal surgery, follow-up of a recurrent partly calcified solid and cystic intra-/supra-sellar craniopharyngioma, low-grade glioma under stereotactic-like conditions, suspected pinealoma, recurrent astrocytoma (II-III) and ganglioneuroma at the posterior aspect of the middle and/or lower brain stem, small scar after lower brain stem infarction, stenosing degenerative disease of the cervical spine and multicystic lesion with an underlying benign ependymoma of the cervical spinal cord. MRI--although duplicating some CT results--provided better two- or three-dimensional anatomical detail as well as display of relevant vessels without need of contrast agent. It also gave more specific information in suprasellar tumours containing fat, afforded uniquely specific diagnosis in a bleeding venous malformation of the midbrain and defined more sensitively extra-/intra-axial lesions of the brain stem and cervical spinal cord. Small bony structures (erosions) and punctate calcifications may be missed by MRI. Although ferromagnetic material distorts the MR image, compared with CT, it is not impaired by non-ferromagnetic clips. This is an advantage with respect to postoperative control examinations.