The dramatic advances in molecular genetics are becoming incorporated into neurobiologic studies at an ever increasing rate. In developmental neurobiology, the importance of cell cell interactions for neurogenesis and gene expression is be ginning to be understood in terms of the molecular bases for these interactions. This book seeks to emphasize the importance of molecular technology in the study of neurogenetic mechanisms and to explore the possible relationships between specific cell cell interactions and regulated gene expression in the develop ing nervous ~stem. This volume consists of nineteen chapters which address ques tions of gene expression and the importance of cell-cell interac tions as key factors in the developing nervous ~stem. Rather than viewing these two processes as separate mechanisms, as the organi zation of these chapters might suggest, we would like to emphasize the interplay of these genetic and epigenetic influences in all phases of neural ontogeny, a concept which is made clear by the subject matter of the contributions themselves. The authors of these chapters were participants in selected ~mposia from the Fourth Congress of the International Society of Developmental Neuroscience held in Salt Lake City, Utah, July 3-7, 1983.