The interaction between lipid vesicles and hydrophobic surfaces (air-water and polymer-water) is evaluated from surface tension measurements, contact angles in air and ellipsometry in situ for determining thickness of deposited molecular films in water. At 50 mM NaCl and 0.2 mM of the cationic dioctadecyldimethylammonium bromide (DODAB) lipid, DODAB adsorption as a function of time yielded an adsorbed layer of 6.0 nm at maximal adsorption onto the polymeric film. The hydrophobic character of the adsorbed DODAB film in air was depicted from advancing contact angles equal to 84 +/- 3 degrees, which were higher than those for the bare polystyrene sulfate film, 71 +/- 4. At SO mM NaCl, 0.2 mM DODAB induced a large decrease of surface tension (from 72 up to 40 mN/m) suggesting NaCl-induced vesicle fusion with the hydrophobic air-water interface. Possibly, NaCl -induced hydrophobic defects in the bilayer vesicle originated vesicle fusion both with the air-water interface (showed by the decreasing in the surface tension) and the hydrophobic polymer-water surface (seen from ellipsometric detection of a deposited molecular film on the polymer surface). NaCl seems to be inducing hydrophobic defects at the DODAB bilayer that are responsible for extensive vesicle fusion with both air-water and polymer-water interfaces.