Wildfires are mainly responsible for economical and ecological disasters both in forests and forest resources all over the world. In this article, we report a method which allows the calculation of risk indices to be used in campaigns designed for preventing and/or fighting forest fires. The method is based on the determination of calorific values using a static bomb calorimeter in oxygen atmosphere following the procedure given by Hubbard et al. [in: F.D. Rossini (Ed.), Experimental Thermochemistry, Interscience Publishers, New York, 1956, p. 5] and flammabilities using the method proposed by Valette [Documentos del seminario sobre metodos y equipos para la prevencion de incendios forestales, ICONA, Madrid, 1988]. A combined study of thermochemical data and bioclimatic parameters allowed the calculation of risk indices for the different species making up the forest vegetation of a zone situated in the coast of Galicia (NW Spain). These risk indices can be presented in the form of maps and, thus, be used to prevent and/or fight forest fires.