This book represents the second part of Integrated Systems of the CNS in the Handbook of Chemical Neuroanatomy. Part 1 was concerned with limbic regions and the hypothalamus, as well as with the retina. Part 11 contains reviews of central pathways associated with four major sensory systems. Future parts will deal primarily with motor systems and the 'reticular core' of the brainstem. It has the been the goal of the authors that each chapter in this volume should provide a current overview of the anatomical organization of the principal functionally defined neural systems in the mammal, as well as what is known about the localization of neurotransmitter-related molecules within them.