Wood samples of the hybrid Eucalyptus grandis x urophylla attacked by white rot fungi were characterized. Microscopically, the colonization of the fungi was observed in the vessels and radial parenchyma, however the cell walls of the some fibers were attacked, indicating susceptibility to this fungi. Zone lines were observed as a result of interaction and compartmentalization of the fungi. Microscopically, the colonization of the fungi was observed in the cell wall of the wood anatomical components, indicating a preferential attack by white rot fungi, with depletion of lignin and hemicellulose. In the zone lines was characterized the formation of a pseudosclerotial structure, with melanized and branched hyphae into a variety of shapes. Analyses of radiographic images were used to determinate variations in density for the eucalyptus decayed and sound wood. In a quantitative evaluation was observed a loss of density in the wood affected by the white rot fungi (mean, minimum and the maximum wood density decrease of 10, 19 and 7,5 %, respectively) demonstrating the possibility of this technique to estimate strength loss in the wood.

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