Childhood abuse is a major public health problem affecting as many as a third of children in this country today at some point before their 18(th) birthday. The effects of childhood trauma on the brain are increasingly an area of interest. In trying to understand the effects of early stressors on the brain we use animal models of early stress to guide the development of hypotheses. An important potential tool in understanding the effects of abuse on the brain is neuroimaging. Neuroimaging studies in traumatized children are in a relative state of infancy. A number of methodological and ethical issues make this a difficult area for research, including problems ranging from patient motion during scanning to the ethical issues of the duty to report abuse and working with child protective services. Some studies have shown that adults abused as children have smaller volume of the hippocampus, a brain area involved in learning and memory, as measured with magnetic resonance imaging (MRI). One study in children with posttraumatic stress disorder (PTSD) did not find smaller hippocampal volume, but did find smaller brain volume and corpus callosum. Functional neuroimaging studies are consistent with alteration in function and structure of medial prefrontal cortex and hippocampus in patients with childhood sexual trauma and PTSD. These initial results suggest that childhood abuse in the setting of PTSD is associated with long-term changes in brain structure and function.