The area of forest land in Finland is 20,085 million hectares. The Finnish National Forest Inventory (NFI) has produced information on forest resources over this area for more than 70 years. The first inventory dates back to 1921-1924. Different forms of damage in statistically representative samples have been registered since the Seventh inventory (1977- 1984). In the Seventh inventory, however, the only identified causes of damage were wind, snow, moose (Alces alces L.) and pine- twisting rust (Melampsora pinitorqua (Braun) Rostr.). The Eighth NFI (1986- 1994) was the first to include more detailed information on health of forests, including diseases and pests. The Ninth NFI started in 1996, and concentrates, in addition to forest health, especially to aspects of multiple use of forests and biodiversity. About 150 stand or tree variables are assessed or measured in the NFI, on more than 70 000 field plots. Satellite images and digital maps have been routinely exploited since the Eight NFI, to produce up-to-date information of forests, and for smaller areas than before. The new inventory method is thus called multi-source inventory (Tomppo 1996).