The gas permeability coefficients K (cm/s) of Newton black foam films stabilized by four alkyltrimefhylammonium chloride homologues have been measured. The experimental results demonstrate well pronounced dependence: K decreases with increasing surfactant alkyl chain length. The temperature dependence of K has been studied as well. The experimental data are discussed on the basis of the nucleation theory of fluctuation formation of holes in the foam bilayers, assuming that the gas permeation occurs both through holes and through hole-free part of the film (background permeability). The mechanism of permeation through the hole-free film is discussed using the theories of monolayer permeability. The results are in favour of the energy-barrier theory.