This volume summarizes the scientific knowledge base on which principles and methods involved in neurotoxicity risk assessment are based. It is aimed at providing a framework for public health officials, research and regulatory scientists and risk managers on the use and interpretation of neurotoxicity data from human and animal studies. It also discusses emerging methodological approaches to studying neurotoxicity. The work examines definitions and critical concepts in neurotoxicity and looks at the criteria for quality of data used in risk assessment. It discusses the structure and function of the nervous system, of the special susceptibilities of the human foetus, children and the elderly, and the types of effects on the nervous system. Progress in developing validated methods for detecting neurotoxicity in humans is investigated, as is the understanding of the factors that affect the validity and reliability of human neurotoxicological studies. There is an extensive review of data derived from experimental animal models, along with an examination of the steps involved in neurotoxicity risk identification, dose-response assessment, exposure assessment, and risk characterization. Overall, this document provides guidance on neurotoxicity risk assessment at a broad international level.