The mammalian central nervous system depends almost - clusively on glucose as its major energy source. In addition, g- cose participates in other cerebral metabolic functions including the biosynthesis of neurotransmitters, such as acetylcholine and the amino acids. This volume of Neuromethods assembles currently available methods for the study of cerebral glucose and energy metabolism in vitro and in mm. In the first chapter, Lust et al. describe the various methods available for the appropriate fixation of brain tissue necessary for the study of cerebral energy metabolism. Different fixation methods are compared, and some concerns raised by the USDHHS in their guidelines for the care and use of laboratory animals are addressed. Specific fixation methods pertinent to the various measurements are also covered in other chapters. In vitro p- parations have, despite certain limitations, been found to be useful in the study of brain metabolism, since the biochemical envir- ment is amenable to rapid, controlled manipulation. The chapter by Lai and Clark describes methods for the isolation and characterization of metabolically active preparations of synaptic and non-synaptic mitochondria from brain, and studies of - zymes involved in glucose metabolism and glucose-derived neurotransmitter synthesis in these preparations are summarized. The chapter by Whittingham discusses methods of preparations of hippocampal slices for use in the study of energy metabolism. Measurement of glucose and of glycolytic and dicarboxylic acid cycle intermediates in neural tissues are described in the chapter by Bachelard.