The study concluded that film-forming polymers having low moisture permeabilities should have the following structural characteristics: 1. Saturated or nearly saturated carbon chain, unless the chain has symmetry permitting high crystallinity; 2. Minimum of chain branching; 3. High degree of lateral symmetry; 4. Very high proportion of relatively small, nonhydrophilic substituents; 5. Fair degree of longitudinal order of symmetry. Extensive table of permeabilities given. 45 ref.