In order to estimate the degree of deterioration of waterlogged woods, the authors measured several physical properties and formed the following correlations between these properties and the hardness of the wood: u = -11.5H + 1390 beta_R = -0.64H + 70 beta_T = -1. 25H + 143 log R1_L = 0.25H 0. 56 where u is moisture content, beta_R radial shrinkage (%), beta_T tangential shrinkage (%), R1_L compr essive stress parallel to grains (kg/cm₂) and H indentation hardness SRIS-0101 (The Society of Rubber Industry, Japan Standard-0101). These correlations are significant over a 1% level. This hardness test is proposed as a non-destructive method of testing the deterioration of waterlogged woods.