Case studies play a vital part in preparedness for major disasters. The first case study involves the bombing of the World Trade Center in 1993 in New York City. A bomb exploded on the B-2 level of the underground parking area of the World Trade Center. The challenges faced by agencies responding to the explosion were that injuries were extensive and numerous, search and rescue efforts had to be carried out all over the complex, on-scene communications were inadequate, telephone lines were flooded, and media outlets were spreading misinformation. The second case study established that today’s terrorists could use chemical agents as well as explosives. Sarin liquid was placed on five separate commuter subway trains at the height of Tokyo’s morning rush hour. Within minutes, people were stricken and Tokyo authorities began a major mass casualty incident response. Over 5,000 people flooded nearby hospitals over the next few hours requiring evaluation and sometimes treatment. The incident was not identified as a nerve agent incident for approximately 3 hours after the attack. Decontamination was not performed on all the victims and riders. Over 50 percent of the victims reported some lingering effects from the attack 5 years later. The third case study is of the bombing of a Federal building in Oklahoma City, killing 168 people. The challenges of this event were enormous. There was an extended crime scene stretching over 200 city blocks that had to be stabilized, secured, searched, and processed for evidence. More than 500 injured persons had to be transported to hospitals for treatment. All of the major damaged buildings had to be searched for survivors. Public safety radio systems were overwhelmed. Information management was critical. Clear command and control was essential to an effective response. Some key points to remember from these case studies are situation assessment takes time, the community will be scared, the incident may involve widespread contamination, and long-term medical/psychological care will be needed.