This volume contains summaries of most of the invited presentations at the NATO Advanced Study Institute "Organizing Principles of Neural Development," held in Povoa de Varzim, Portugal, from June 1-12, 1982. The meeting was intended to bring together a select group of investigators to present their views on problems in the field and to foster extensive discussions in smaller groups. It was hoped that such communications would pique curiousity and creativity among the students and thus help in formulating additional hypotheses regarding the type of interactions which might underlie neural development. Despite the wide range of material covered at this institute, a common theme seemed to emerge: at all stages of their develop mental history, the cells of the nervous system interact with previously generated cells (both neurons and non-neurons) as well as with other constituents of the developmental milieu. The pre sentations at this meeting helped in comprehending how a relatively "simple" series of sequential events might provide the necessary information needed to generate the diversity, characteristic of the adult nervous system, without hypothesizing on the existence of specific genes acting to control each step."