Much has happened since publication of the previous volume (71) on neural regeneration in this series in 1987. Some of the progress in research in this field is reflected in the present volume, which incorporates the proceedings of the Fifth International Symposium on Neural Regeneration held in California in December, 1993. This current volume is organized into six topic sections. Subjects covered include Neurotrophins and Receptors, Calcium and Gene Expression and Nitric Oxide in the Central Nervous System. The first chapter in each section, whose title reflects that of the section heading, is an introduction to and an overview of the topic. The highlights of the Symposium presented here reflect some of the more important recent advances in neural regeneration research, such as characterization of the increasingly complex family of the neurotrophins and their receptors, definition of the molecular mechanisms that encourage and guide axon growth, including immediate early gene activation and calcium signals, and elucidation of the many ways in which the nervous and immune systems are interactive. The section on models of spinal cord regeneration is phylogenetically organized to provide comparisons between lower animals that can and higher animals that cannot regenerate their spinal cords. There are no illusions that all aspects of neural regeneration are addressed in this volume, but the rich sample presented here should give the reader a strong sense of the excitement and the hope that have come to pervade this field.