BACKGROUND: On May 4, 2007 an EF5 tornado hit the rural community of Greensburg, KS, destroying 95% of the town and resulting in 12 fatalities. METHODS: Data was requested from the emergency medical services units that initially responded and the regional hospitals that received people injured in the tornado within 24 hours following the tornado. Requested data included patient age and sex, and injury severity score or ICD-9 codes. Critical mortality, or the number of deaths of critically injured patients, was also calculated. RESULTS: The extensive damage caused by the tornado effectively destroyed the infrastructure of the community and created enormous challenges for emergency medical services responders, who were unable to record any triage data. Area hospitals treated 90 patients, who had an average injury severity score of 6.4. Age was found to be related to injury severity, but no relationship between sex and injury severity was found. Critical mortality was found to be 18% for this event. CONCLUSIONS: Injury severity score has seldom been used to analyze natural disasters, especially tornadoes, although such analysis is helpful for understanding the magnitude of the disaster, comparing to other disasters, and preparing for future incidents. Advanced warning and personal preparedness are important factors in reducing tornado-related injuries and deaths.