During the last ten years clinical neurophysiology has used computerized quantitative methods for analysis. Evaluation of the information previously hidden in the signals from the nervous system offers previously unknown uses and applications for neurosurgery. The quantitative EEG (QEEG) for example may offer more reliable and easily understandable information of brain activity than the conventional analogue EEG. The techniques for QEEG-analysis have now reached such an advanced stage that they extract at the same time more information from the EEG than can be achieved by visual interpretation. The problems of distances between neurosurgical departments and computer centers can be overcome by means of telephone transmitter systems, as has been done in the present study. Patients with epilepsy or brain tumour undergoing surgery were analyzed and monitored with the peroperative tele-QEEG-system. Our experiences were encouraging since the neurophysiological part of the work at the operation unit was reduced considerably thanks to the tele-system. At the same time we obtained easily understandable EEG-information which has never previously been available to us.