Trauma in the form of natural disasters, war, and other catastrophic events is ubiquitous. Exposure to traumatic events has been recognized as part of the human experience and has the potential to impact subsequent development across the life span, although individual responses to trauma vary widely. In this chapter, we discuss common sources of trauma and their long-term impacts from the perspective of conservation of resources (COR) theory. In brief, COR theory posits that traumatic stress is a dynamic psychological process that occurs in response to the rapid and often momentous loss of key valued resources. COR theory corollaries include the notions that loss is developmental and tends to occur in negative spirals, the impact of loss outweighs the positive impact of gain, and individuals with fewer reserves of resources are more sensitive to loss and gain (Hobfoll, Stress, culture, and community: The psychology and philosophy of stress, 2004). Common reactions to trauma such as posttraumatic stress disorder (PTSD) are introduced with an emphasis on how reactions unfold over time. Moreover, these reactions interact with the broader social context to produce cycles of loss observed at the individual, community, and cultural levels.