The mechanical properties of 4 timber species (poplar, fir, pine and hornbeam) commonly used in Turkey were investigated. The compressive strength, flexural strength and toughness were determined both perpendicular and parallel to the grain. The modulus of elasticity of timber specimens was also determined parallel to the grain for the compressive test and perpendicular to the grain for the flexural test. It was found that loading direction affects all mechanical properties remarkably. Among the timbers tested, maximum and minimum mechanical performances were obtained with the 2 hardwoods, i.e. hornbeam and poplar, respectively. The mechanical performance of the softwoods, i.e. fir and pine, was between that of the 2 hardwoods. Hornbeam showed the minimum anisotropy. Except for hornbeam, the timbers showed very low compressive strength when loaded perpendicular to the grain and very low flexural strength when loaded parallel to the grain. ©TÜḂ ITAK.