The effects of aging in wood in term of physical, mechanical and chemical degradation has been studied first by Jiro Kohara [1] and more recently by Erhardt et al. [2-3] and Obataya [4]. It has been observed that similar degradation can be found in thermo-hydro (TH) treated wood [4]. The aim of this study is to compare the mechanical behavior of naturally aged and accelerate TH wood in the radial direction. A first pressure vessel with controllable temperature, oxygen pressure and relative humidity has been designed and constructed. The temperature and relative humidity range are 100 to 150 °C and 2 to 100% of RH respectively. This pressure vessel is able to maintain the conditions constant for long term processing. A second pressure vessel, using a vapor heating system, has been used to test higher temperature range (120 to 200 °C). The amount of oxygen cannot be set in this last thermal cell. Different types of thermo-hydro treated wood have been done with these machines.