The most common cause of death in fires is the inhalation of noxious gases rather than thermal injury. Hydrogen cyanide gas, the most toxic product of combustion, seldom is recognized as a significant hazard in smoke inhalation. During the first four months of 1986, toxic amounts of cyanide were found in four of the six fatalities from house fires in Akron, Ohio. These cases illustrate the increasing frequency of cyanide poisoning in household fires. Sources of cyanide toxicity include the increased use of synthetic polymers in building materials and furnishings. Prompt recognition of and therapy for cyanide intoxication may reduce the morbidity and number of delayed deaths in fire victims. The key point in the diagnosis of cyanide poisoning is a high index of suspicion. The clinical presentation of cyanide intoxication, its diagnosis, and subsequent treatment are discussed. Finally, a prehospital protocol for treating smoke-inhalation victims who may have been exposed to cyanide gas is suggested.