Data are given on moisture permeation of leather and plastics exposed both to water and water vapor. The rate of moisture permeation of some plastics is equivalent to that of some leather now used. The permeation of moisture through leather depends upon the tannage, and by adopting the proper tannage could be greatly increased. However, leathers that are highly permeable to water are not practical for use in shoes, and in this respect man-made materials will undoubtedly be able to compete with leather. Other properties, such as insulation and ability to mold to the feet, are characteristics which will continue -- AATA