The mechanical properties were determined of timber from three cultivars of Populus x euramericana (cv.I-72, cv.I-161 and cv.I-488) growing in the province of Valdivia in 1976. The mechanical properties were determined at 12% moisture content according to the Chilean standards specific to each type of characteristic. According to the species grouping procedure, by strength, established in the Chilean Standard 1989, the three varieties belong to the group ES 6, a group to which belong Populus nigra, Pilgerodendron uvifera and Saxegothaea conspicua. The average values of mechanical strength are slightly lower than those of Populus nigra.