Forestry in Galicia has experienced a large change from the middle 1980s as a consequence of an aggressive forest exploitation due to the introduction of fast growing forest species to be used as raw material for production of pulp. Owing to its easy adaptability to Galician environment, eucalyptus is one of the forest species mostly used. Nowadays, the forest surface covered eucalyptus is close to 240 000 ha. Residues originating from forest exploitation of this species, together with changes experienced by the forest ecosystem cause important environmental problems, amongst them forest fires and environmental wildness. This study was focussed on the determination of risk indices of the biomass originating from eucalyptus residues. These indices indicate the capability for these residues to start and spread forest fires and can be used to design campaigns to prevent and/or to fight forest fires. The determination of risk indices includes measurements of flammability, using an epiradiator following the standard UNE-23-721, and caloric values using a static bomb calorimeter. Different parameters necessary for understanding these risk indices, such as elemental chemical composition (Carlo Erba elemental analyser), biological, and environmental parameters were also determined. The study was performed over 1 year, in three different zones situated in Galicia.