United States Army researchers have developed an instrument for measuring the transport of water vapor through coated and uncoated fabrics, fabric laminates, thin foams, and solid films. The apparatus incorporates an automated dynamic moisture permeation cell (DMPC) to allow multiple setpoint testing under computer control and to facilitate investigation of transient phenomena. The DMPC apparatus is more convenient to use than traditional test methods for textiles or apparel fabrics because it uses a wider variety of test conditions to investigate the concentration dependent and nonlinear transport behavior of many semipermeable membrane laminates. Experimental data generated with the DMPC are in agreement with and of comparable accuracy to those from the ISO 11092 method (sweating guarded hot plate) method of measuring water vapor permeability. 23 resfs.