Lesions of the brain stem and related disorders of autonomous regulation systems have been the "Leitmotiv" of the scientific work in the Neurosurgical Department of the Giessen University under the leadership of the late Professor Hans Werner Pia. Some of the results have already been published in supplement volumes of Acta Neurochirurgica. The first one of these was Vol. 4 with the monograph written by H. W. Pia on "Die Schadigungen des Hirnstammes bei den raumfordernden Prozessen des Gehirns." Vol. 19 deals with central disorders of temperature regulation, written by G. Lausberg, followed by Vol. 20 with R. Lorenz's monograph on the effects of intracranial space-occupying lesions on blood pressure and heart rate. Shortly before his death Hans Werner Pia had asked me to combine and publish in this series of supplement volumes of Acta Neurochirurgica another five papers by his co-workers, also related to brain stem lesions and also to cerebral blood flow and CSF dynamics. The result is this volume which contains work dealing with the CT -findings of cerebral mass displacements and their clinical correlations (Sch6nmayr), with other lesions of the brain stem (Laun), with the blink reflex and acoustic evoked potentials in brain stem lesions (Klug and Csecsei), with blood flow in brain structures during increased ICP (Zierski) and with the description of a mathematical model for analysis and simulation of the haemodynamics of intracranial CSF (Hoffmann).