By decreasing blood viscosity and vascular resistance normovolemic haemodilution increases cerebral blood flow and improves microcirculation. This eliminates the symptoms of anoxia of cerebral tissue. The extent of disturbances of the blood brain barrier is decreased. The case presented in this paper illustrates the use of the above-mentioned properties of haemodilution and concerns a patient with chronic subdural haematoma. The patient's status in the pre-operative period was very poor. Craniotomy and avacuation of the haematoma did not result in a visible improvement of the patient's state. He did not regain consciousness and even lost spontaneous respiratory function. Haemodilution /Hct 29%/ was performed using Dextran 60 and 5% human albumin in the proportions 1 : 1. As a result, spontaneous respiration was restored and there was a gradual improvement in the patient's status. 29 days later it was possible to communicate with the patient. The authors are of the opinion that haemodilution could find a much application in neurosurgery than has been the case up to now.