The manner in which the permeability of unsaturated porous materials varies with moisture content has been investigated, using an electrical analogue technique. The hydraulic resistance of a water channel in the porous material has been represented by an electrical resistor, and the three dimensional network of channels by a corresponding three dimensional resistance network. With all the resistors in circuit the electrical resistance across opposite faces of the network is assumed to be inversely proportional to the saturated permeability. Empty channels are not effective in transporting liquid so that drying of the material is simulated by progressively removing resistors representing the largest of the remaining water-filled channels. In this way the decreasing permeability of the material as it dries out can be related to its moisture content. The predictions by the analogue method agree very well with the experimentally determined values.