The article deals with the problem of radioactive forest fires. Authors noted a need to clarify the qualification criteria of forest fires as radioactive and creating their classification. As a criterion for the hazard of radioactive forest fires, the parameters of the minimum significant activity (MSA) and the minimum significant specific activity (MSSA) in forest fuel (combustible) materials (forest litter) for cesium-137 are used, as applied to the fire edge. An approach is proposed for classifying radioactive forest fires on the basis of data on the density of radioactive contamination of forest areas and types of forest conditions. A variant of the scale of categories of radioactively contaminated forest sites and radioactive forest fires (the hazard levels for the prevention and extinguishing radioactive forest fires) is proposed.