A nuclear magnetic resonance (NMR) machine constructed by Thorn-EMI Ltd was used to produce tomographic images of the brain in eight volunteers and fourteen patients. The use of an inversion recovery technique designed to emphasise variations in the spin-lattice time constant (T1) resulted in remarkable differentiation between grey and white matter in all subjects examined. White matter was seen both centrally and peripherally to subcortical level and the basal ganglia were clearly demarcated by the surrounding white matter and ventricular system. The posterior fossa was visualised with substantially less artefact than with X-ray computed tomography (CT) and both the brainstem and middle cerebellar peduncle were clearly shown. Pathological appearances in patients with glioblastoma multiforme, cerebral infarction, and cerebral aneurysm were demonstrated and compared with those seen with CT. The technique will require thorough clinical evaluation but appears to have considerable potential in the diagnosis of neurological disease.