With regard to the high mortality of silver fir (Abies alba Mill.) in Italy, pathological and climatic causes are considered crucial, while soil properties are usually neglected. Two of the largest Tuscan forests of this species, the one of Vallombrosa and the other of Mount Amiata, are seriously affected by Heter obasidion annosum, a fungus causing root rot. However, in spite of the same provenance of firs and intersterile group of the fungus, the tree death is different at the two sites. In one case, firs quickly died standing, while in the other they were uprooted after a slow course of the illness. A study Nas conducted on the two localities to perceive the role of soil properties in this connection. In the light of our results, pedological conditions are important, negatively affecting the plants either "directly" - limiting deep rooting and preventing the trees to achieve sufficient anchorage in the ground - and "indirectly" - favouring the sp read and the virulence of H. annosum.