In early development, there are critical periods, such as prenatal, perinatal, and pubertal periods, during which chemical, biological, and physical insults (i.e., nutritional restriction, maternal stress, etc.) exert permanent alterations on physiology, metabolism, and health of off spring [1]. Although most people are able to cope with stressful events and only display a brief stress response with heightened physiological activity before stress recovery, exposure to stressful events during these critical periods can lead to the development of long-term psychopathological conditions in a significant number of people [2]. A complex interplay between genetic and environmental factors is probably at the origin of this heterogeneity. These proceedings are based on a workshop session at the US-South America Workshop in Neuroendocrinology. The session was based on the diverse effects of exposure to stressors during critical periods of development. Therefore, in these proceedings, we discuss the effects of exposure to a stressor during critical periods of development on mental health, sexual differentiation, behavior, metabolism, and gene expression in the brain. These proceedings are not meant to be a comprehensive review of the literature. It is simply meant to bring together the diverse effects presented during the workshop.