A method is proposed for calculation of risk indices of different forest formations existing in Galicia. These values are helpful to predict the behaviour of forest species in case of forest fires and thus to prevent and/or fight these wildfires. Main parameters for calculation of risk indices are calorific values measured by bomb calorimetry and flammability measured by a standard epiradiator. These parameters were studied together with chemical analysis of different forest samples and an intensive research of physical and environmental parameters. All the data presented were determined in the last 10 years in Galicia (NW of Spain). (C) 2004 Elsevier B.V. All rights reserved.