Previous experimental studies caution against the use of neurolept anaesthesia during subarachnoid injection of metrizamide for neuroradiodiagnostic procedures because of severe epileptogenic complications. To examine whether these recommendations are relevant in the clinical situation or not, 104 patients were studied. They underwent neuroradiological investigations with metrizamide subarachnoidally and were anaesthetized with neurolept anaesthesia either during the investigation (59 patients, Group I) or within 48 h afterwards (45 patients, Group II) when a neurosurgical operation was performed. In 10 patients of Group I, EEG was recorded during the investigation. All patients were observed for occurrence of clinical epileptic manifestations during and after the anaesthesia. Apart from one patient who had a short episode of suspected epileptogenic EEG-activity shortly after the injection of metrizamide, none of the other patients showed EEG-abnormalities of epileptogenic type and none of them had any clinical signs of epileptic manifestations. On the basis of the results of this clinical study it is concluded that neurolept anaesthesia does not increase the risk of epileptic complications during neuroradiological investigations with metrizamide.