Severe childhood trauma appears to play an important role in the development of various psychiatric syndromes. Multiple personality disorders, somatization, anxiety, and posttraumatic stress disorders appear to be strongly associated with previous trauma, such as childhood sexual abuse. In other disorders, such as affective disorders, attention deficit hyperactivity, and substance abuse, genetic and biological factors, psychosocial forces, and previous trauma appear to interact with varying primacy from case to case. The precise etiology of most emotional and behavioral dysfunction is probably not either trauma or biological predilection alone, but rather determined by the interaction of these and other factors. Studies that include psychophysiological, biological, and psychosocial instrumentation offer the greatest potential for increasing knowledge about factors contributing to psychiatric dysfunction.