Abstract On July 8, 1986, local, state, and Federal personnel responded to a train derailment and subsequent fire of a tanker car containing white phosphorus in Miamisburg, Ohio. For a period of 5 days, fire departments from Miamisburg and up to 14 nearby communities fought the fire, which was caused by the gradual release of 12,000 gallons of air-reactive white phosphorus. During this period, approximately 30,000 area residents were evacuated and 166 people were treated at local hospitals. Response support was provided by numerous agencies/governmental units, including: the city of Miamisburg; the Dayton Area Hazardous Materials Team; fire departments in Montgomery County; The Miami Valley Disaster Services Authority; the Ohio Environmental Protection Agency; the U.S. Environmental Protection Agency; the Roy F. Weston Technical Assistance Team; the U.S. Department of Transportation; and the American Railroad Association. Initial support was focused on protecting the public health and welfare and on maximizing containment of the released materials. Subsequent to extinguishing the fire, large-scale cleanup operations commenced that included the treatment of contaminated water, soil, and river sediments. This paper summarizes these efforts and discusses the activities taken by the major agencies involved in the rapid response to the incident in Miamisburg, Ohio.