The dieback of European beech trees has occurred in the northeast of Romania since 2000, but beech decline has also been noticed in other regions. The disease factors have been recorded in 11 experimental plots (of which 6 permanent) and along different transects. The most important decline factors seem to be the climatic conditions (drought of 1999-2000), stand characteristics (age, proportion of beech in stand composition), landform (especially plain sites), soil characteristics (excessive clay or sand content), associated (bark and wood) fungi and insects.