The froth stability of aqueous solutions of non-ionic surfactant was found to decrease on addition of low concentrations of KCl but increase at higher concentrations. From earlier reported studies on free aqueous films, it could be suggested that two different types of stabilizing mechanisms were operating in the froth system. At low electrolyte, the decrease in froth stability was explained by the decrease in interfacial electrostatic repulsion force while at high electrolyte, the enhanced stability was accounted for by steric forces.