That the strength properties of wood and wood-base materials are influenced by duration of stress has long been recognized, both in the use of design stresses and through the establishment of rate of loading requirements in standard test methods. This paper presents a summary of recent data that supplements the information presented by the authors at the 1948 ASTM symposium on the same subject (4). Extensive data have been obtained on the effect of rate of loading on the compression-parallel-to-grain and flexural strength properties of two hardwood and two softwood species. The similarity of trends obtained from short-time and long-time tests indicates that the relationship between ultimate strength and time can be presented in a simple curve from load durations of a fraction of a second to many years. Values for modulus of elasticity remain substantially constant irrespective of rate of loading. Data are also presented to show that the flexural strength of building fiberboards of the densities tested is increased as the rate of loading is increased. Further tests are necessary, however, to establish more precisely the magnitude of this effect for fiberboards. Additional studies are needed further to determine, for both wood and wood-base materials, the influence of rate of loading on other mechanical properties, and to provide more substantial data on the effect of loadings extended over many years.