The effect of the Gibbs elasticity on foam stability was investigated using tetraethyleneglycol-octylether (C8E4, a non-ionic surfactant) and tetrapenthyl-ammonium bromide (TPeAB, an antifoaming agent). The surface tension isotherms for the aqueous solutions of C8E4, TPeAB and their mixtures (C8E4 + 0.01 M TPeAB) were measured by the Harkins-Brown drop method. The Gibbs elasticity as a function of the surfactant concentration was determined using the surface tension data and the Szyszkowski-Langmuir adsorption theory. The foam stability for the C8E4 and C8E4 + 0.01 M TPeAB solutions was measured by the foam lifetime by the shaking method. The results showed that the foam was stable above a minimum of Gibbs elasticity. The presence of TPeAB in the adsorption layer reduced the Gibbs elasticity and the foam stability. Therefore, a higher concentration of C8E4 was needed for producing a stable foam. The Szyszkowski-Langmuir adsorption theory was also successfully applied to the surfactant mixtures to predict the effect of the Gibbs elasticity on the foam stability. A good correlation between the Gibbs elasticity and the foam stability was obtained for the surfactant systems.