Eight normal volunteers and 32 patients with a variety of neurological disease were studied with a nuclear magnetic resonance (NMR) scanner using repeated free induction decay (RFID), inversion-recovery (IR) and spin-echo (SE) sequences. The results were compared with X-ray computed tomography (CT). RFID sequences which produce images that reflect changes in proton density displayed very little grey-white matter contrast and relatively small changes in disease. IR sequences which produce images that are dependent on T1 showed a high level of grey-white matter contrast and demonstrated changes in a variety of pathological processes. Although SE scans, which have a strong T2 dependence, had shown no abnormality in previous studies of patients with neurological disease, sequences of this type with longer values of tau displayed abnormalities in cerebral infarction, haemorrhage, herpes encephalitis, multiple sclerosis, cerebral oedema, hydrocephalus, tumours and Wilson's disease. All of these conditions were associated with an increase in T2. Abnormalities were demonstrated in cases of multiple sclerosis and brainstem infarction with NMR scans where no abnormality was seen with CT. More extensive changes were seen with NMR in cases of hemisphere infarction, systemic lupus erythematosis, herpes encephalitis, hydrocephalus (periventricular oedema) and Sturge-Weber disease. The margin between malignant tumour and surrounding oedema was better defined with contrast enhanced CT in four of eight malignant tumours, equally well defined in one, and better defined with NMR in three cases. NMR spin-echo sequences provide a sensitive technique for detecting abnormalities in a variety of neurological disease.