The knowledge of the factors involved in the water transmission through collagen fibrous network of skin and leather is essential in the manufacture of materials that will give improved service and maintain a sufficiently high level of breathability and permeability to assure comfort to the wearer. The study of the structure and connectivity of the pores in the skin and leather is essential since it influences the heat and mass transport processes. This research study focuses on the porous structure and water vapor permeability of animal skin after it has been subjected to different treatments, such as pickling or tanning with chromium salts, or vegetable tannins. The obtained data indicated that surface groups, inorganic matter, and pore size distribution have influence on the water transmission. Water vapor adsorption isotherms showed pickled skin to have a greater adsorption capacity at a higher relative humidity, whereas vegetable-tanned leather was found to be the sample with the lowest adsorption at higher relative humidity probably due to its greater density, lower accessibility of the functional groups, and wider distribution of pore sizes than the other materials. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1812-1822, 2013