A model has been suggested which allows the calculation of stresses arising in kiln drying and humidification of wood, as well as the total residual strain, i.e. “set strain” ɛs, consisting of purely residual strain ɛr and the so-called “frozen strain” ɛf. Frozen strains arise under the operating influence of loading when the stiffness is increased because of a decrease in moisture content (or temperature) of the wood. The process of formation of set strains ɛs has been shown to depend on the history of loading, variations of the moisture content of the wood, as well as cooling of the section before the measurement of ɛs. The possibility of using set strain as a parameter of the state of stress of wood in kiln drying has been noted.