In the aftermath of the deaths of 14 firefighters during the South Canyon Fire in July 1994, fire scientists assessed what occurred and suggested guidelines that may help firefighters avert such a tragedy in the future. This report describes the fuel, weather, and topographical factors that caused the transition from a relatively slow-spreading, low-intensity surface fire to a high-intensity, fast-spreading fire burning through the entire fuel complex, surface to crown. The analysis includes a detailed chronology of fire and firefighter movements, changes in the environmental factors affecting the fire behavior, and crew travel rates and fire spread rates. Eight discussion points apply directly to firefighter safety.