A new diffusion cell, derived from the Ussing chamber, was developed for the measurement of tissue permeability. This cell incorporates the attributes of using a single material and laminar flow across the tissue surface. In addition, the design allows the cell to be manufactured in a wide range of sizes to allow optimization of surface area to volume for a variety of tissues. The apparatus is applicable to the evaluation of transport of compounds through mucosal/epithelial barriers, i.e., gastrointestinal tissue. Active transport, permeability enhancers, enzymatic degradation, and absorption in various tissue sections can be explored. Preliminary data are consistent with the expected effects of molecular size and partition coefficient of a transported molecule on permeability in epithelial tissue. In addition, active transport of D-glucose and inhibition by phloridzin and ouabain can be demonstrated.