Two apparatuses for measuring the specific permeability of wood specimens are presented. The developed method was used to measure specific permeability to water in the longitudinal direction (of the log) for three wood species, pine (Pinus sylvestris), birch (Betula pendula), and eucalyptus (Eucalyptus grandis). The wood species were cooked to a certain degree Under kraft cooking conditions. The effect of pretreatments on the specific permeability of uncooked wood was also studied. These pretreatments include boiling in water, steaming, and impregnation with cooking liquor. wood species were cooked to it certain degree with an H factor of up to 600 for pine, 376 for birch, and 400 for eucalyptus, The average specific permeabilities to water ranged from 1 x 10(-13) to 3 x 10(-12) m(3)/m for cooked pine, from 1 x 10(-13) to 1 x 10(-12) m(3)/m, for cooked birch, and from 3 x 10(-11) to 5 x 10(-11) m(3)/m for cooked eucalyptus.