Functionalized silanes are widely used as protective coatings and interface coupling agents.  Certain bis silanes, for example, are effective anti-corrosion agents.  In virtually every application, the longevity of the film is a key performance parameter.  Here we use neutron and x-ray reflectivity to study the hydrothermal response of bis-silane films.  Of particular interest is the response of silanes with amine and poly sulfur bridging groups as well as mixture of these silanes.  The mixture is known to afford better protection than either of the neat silanes.  Films were first studied at room temperature–dry, in the presence of D₂O vapor and in the presence of liquid D₂O. These studies showed considerable water penetration, but minimal degradation.  The amino-bridged film showed unusual behavior in that the film in contact with liquid D₂O  swelled less than when in contact with D₂O vapor.  These films were also hydrothermally conditioned in H₂O for various time periods at 80 C.  Surprisingly, the hydrophilic amino film showed less degradation than the hydrophobic sulfur bridged film.