Increasing evidence supports the view that the interaction of perinatal exposure to adversity with individual genetic liabilities may increase an individual's vulnerability to the expression of psycho- and physiopathology throughout life. The early environment appears to program some aspects of neurobiological development and, in turn, behavioral, emotional, cognitive, and physiological development. Several rodent and primate models of early adverse experience have been analyzed in this review, including those that “model” maternal separation or loss, abuse or neglect, and social deprivation. Accumulating evidence shows that these early traumatic experiences are associated with long-term alterations in coping style, emotional and behavioral regulation, neuroendocrine responsiveness to stress, social “fitness,” cognitive function, brain morphology, neurochemistry, and expression levels of central nervous system genes that have been related to anxiety and mood disorders. Studies are underway to identify important aspects of adverse early experience, such as (a) the existence of “sensitive periods” during development associated with alterations in particular output systems, (b) the presence of “windows of opportunity” during which targeted interventions (e.g., nurturant parenting or supportive–enriching environment) may prevent or reverse dysfunction, (c) the identity of gene polymorphisms contributing to the individual's variability in vulnerability, and (d) a means to translate the timing of these developmental “sensitive periods” across species.