The aim of this study was to evaluate the vaporization effects on the crushing strength at limit of proportionality on perpendicular compression, crushing strength and modulus of elasticity in parallel compression to the fiber and shear strength (radial and tangential direction) on logs and sawn wood of two sources of Eucalyptus dunnii. The mechanical attempts were performed under the Copant standards in the climatized conditions (12%). To do so, about two thirds of the logs, with a diameter between 20-30 cm, were vaporized at 100o C and 100% of relative humidity for 20 hours, while the remaining logs were kept as control. From each log, a central plank radially directed with eight centimeter of thickness was taken, from which small beams of 8 cm x 8 cm were taken. Half of the small beams from the vaporized logs were once again submitted to vaporization under the same previously described conditions for a period of 3 hours, thus obtaining three different levels of comparison (control, vaporized on logs and presteaming wood). The results showed a remarkable reduction on the crushing strength in parallel compression to the fiber and shear strength (radial and tangential direction) with the vaporization on the two conditions and sources of Eucalyptus dunnii used. On the other hand, the crushing strength at limit of proportionality on perpendicular compression and modulus of elasticity in parallel compression did not show any change with the vaporization.