This Report is a technical comparison of the American and Canadian systems of forest fire danger rating. It deals with the three fuel moisture indicators in each system, as well as the indexes of spread and energy release or buildup. The final comparison is between the American family of Burning Indexes and the Canadian Fire Weather Index. The American system has, relative to the Canadian, faster fuel drying, less variation of spread rate and intensity with fuel moisture, and less response to rain; it contains no slow—drying moisture indicator such as the Canadian Duff Moisture Code or Drought Code. The American system is judged best suited to grassy, open forests, and the Canadian system to forests with fairly full canopy and substantial duff layer.