The amount of moisture transmitted under four different humidity conditions was measured in earlywood and latewood for Cryptomeria japonica(LT specimens). The results obtained are summarized as follows. The vapor permeability in eariywood was about three times larger than that of latewood. The vapor permeabilities in earlywood and late wood depended on the average moisture content of the wood. This indicates that moisture transmission is influenced by vapor permeability or vapor-transmission resistance, but the values obtained by experiments do not have great adaptability for practical situations because of changes in the experimental conditions. There fore, it is necessary to know the moisture content along the flow direction in order to explain the moisture transmission of wood. The vapor permeability was calculated using the density in air dried wood. These were then compared with the experimental values. The vapor permeabilities calculated with this density in the radial direction(LR specimen) had a good tendency to agree with the experimental values, but not so in tangential direction(LT specimen).