Intended for teachers of young children exposed to violence in their communities, this paper presents an introduction to post-traumatic stress disorder (PTSD), including its definition, symptoms, causes, and providing a supportive classroom environment. The definition discussed is based on that of the Fourth Edition of the Diagnostic and Statistical Manual of Mental Disorders, as are the listed criteria for diagnosing PTSD. Other aspects of PTSD discussed include re-experiencing the traumatic event, avoiding reminders of traumatic events, symptoms of increased arousal, and clinically significant distress. A section on working with children diagnosed with PTSD notes additional symptoms a teacher might see in the classroom, such as hyper and hypovigilance and increased sensitivity to sound and touch. Classroom guidelines address helping the child learn to feel safe in the classroom, activities that promote safety, responding to developmental delays caused by PTSD, the role of the classroom staff with the child and family, behavioral issues, individualizing behavior management, setting limits in the classroom, making a referral, and working with the family and professionals. (Contains 17 references.) (DB)