The leading cause of neonatal mortality is birth defects, in some cases the result of exposure to neurotoxins. Even when not resulting in death, damage to the developing brain or central nervous system as a result of exposure can result in negative impacts that affect lifelong outcomes. Genetic conditions, medical conditions, and trauma are most often discussed as identified causes for neurodevelopmental disorders and damage to the brain. Neurotoxins, or harmful substances, that can affect brain function and development from conception onward further add to risk for deviations from typical development and optimum outcomes. This chapter introduces the context of neurotoxins and the mechanisms by which in utero and postnatal exposure can affect neural development and function. At the same time that advanced technology allows research to better understand brainbehavior relations and various neurotoxins, the potential for exposure to neurotoxins with deleterious effects also is increasing. Other moderating factors are identified, as well as general considerations for prevention and intervention.