A decade has passed since systematic studies were initiated in the USA in an attempt at establishing the experimental basis for a surgical technique which was to prove an effective tool in combatting one of the most common diseases, i.e. cerebrovascular accidents. The development of such intricate vasculosurgical techniques as are required for extra intracranial arterial bypass operations would not have been possible without the aid of the surgical microscope, which had been designed some years earlier. In the past few years increasing emphasis has been placed on establishing clear-cut indications for the bypass operation, because satisfactory long-term results are unlikely to be obtained without them. Needless to say that this requires a close cooperation of the neurosurgeon with a team composed of neurologists, internists, radiologists, and pathologists. Fortunately enough, cooperation between the services of the University of Vienna Medical School proved to be exemplary. While there has been no lack of efforts by major medical centers both in Europe and the overseas countries to perfect bypass operations for cerebrovascular accidents, a comprehensive monograph reviewing all medical and operative problems involved in microvascular surgery for strokes was badly missed by many. von Kletter, G.