Risk indices for the different forest species existing in a high mountainous zone situated in Galicia (NW Spain) as well as their seasonal evolution were studied. Calculation of these risk indices was based on the previous elaboration of energy maps from mean calorific values, flammabilities and chemical analyses of forest species. A combined study of energy maps, bioclimatic characteristics of the zone and main biological properties of the different species led to the determination of the seasonal risk indices. Knowledge of risk indices of the species allows the design of maps to be used to prevent and/or fight forest fires.