The effects of moisture and strain rate on the tensile properties of poly(hydroxy eater ether) (PHEE) were investigated. Water was shown to act as a plasticiser which lowered the room temperature tensile strength and modulus. The strain at failure increased with increasing water content and a change in the mode of failure was observed. Brittle failure occurred when the moisture content was low. As the sorbed water content increased, the samples necked and extensive plastic deformation resulted. The samples deformed in a quasi-homogeneous manner at testing temperatures close to the glass transition temperature. The yield stress decreased with moisture content and increased with strain rate. For samples which deformed in a ductile manner, the variation in the yield stress with strain rate was well described using the Eyring model. The effect of water content on the yield stress was shown to be analogous to the effect of temperature.