T IlE purpose of this invest igat ion was to emnpare the glycolytic response of nmlignant a s t rocy tomas to tha t of the h u m a n brain (white mat te r ) when incuba ted under anaerobic conditions. Cerebral tissue rapidly reacts to oxygen depr ivat ion b y degrading glucose and glycogen to form an equivalent amoun t of lac ta te (two equivalents of lacta te per equivalent of hexose expended)2 Glycolysis in the malnmal ian brain thus follows a well-defined anaerobic sys tem (the Elnbden-M:eyerhof pa thway) to provide a shor t te rm emergency source of energy for the ischemic brain. Glycolysis in itself, however, cannot fulfill the energy denmnds of an ischemic brain for more than a few minutes2 This general biochemical response of tissue to oxygen wan t is known as the "Pas t eu r effect," and has been the subject of intensive invest igat ion in murine brain by Lowry and co-workers, v Prolonged ischemic incubat ion (more than 1 hour) is not associated with any fur ther glyeolytic ac t iv i ty in the routine brain, bu t has not been invest igated in the h u m a n brain3 Neoplast ic tissue differs nmrkedly from oxygenated m a m m a l i a n brain in tha t it produces lactic acid excessively even during aerobic conditions, n The exceptional abil i ty of neoplasms to produce lac ta te undergoes still fur ther augmenta t ion during ischemic incubation. 1 Thus , tumors in general, and human brain tumors in par t icular, demons t ra te a clear-out Pas t eu r effect. In this study, two glioblastomas and companion samples of white m a t t e r were incuba ted anaerobically for periods of t ime ranging f rom 5 minutes to 4 hours. Di rec t quantita t ion of major glyeolytic metabol i tes and co-factors a t varying intervals of anaerobic incubation permit ted an accura te es t imate