SUMMARYWe have isolated the lowest region of human and pig stratum corneum as an integral layer which we have termed the stratum compactum. This preparation is resistant to disruption by enzymes, 6murea, Triton X‐100 and solvents. Our evidence suggests that all cells of the stratum corneum may be equally permeable to aqueous soluble materials but that penetration of materials through the corneum depends on the state of cohesion between cells and of the organization of intercellular lipid species. As the cells move up towards the outside of the stratum corneum the cohesive forces are reduced due to desmosome degradation and lipid modifications with ultimate dyshesion and sloughing of individual cell