The rate of collapse of a foam column was measured for foams generated from alkaline solutions of a common anionic and a common nonionic surfactant containing small drops of hexadecane, triolein, and their mixtures with oleic acid. Observations of drainage and rupture of individual foam films and measurements of surface and interfacial tensions were also carried out. When dissolved calcium was present and the oil contained oleic acid, particles of calcium oleate formed during the experiment and, in many cases, destabilized the foam by facilitating entry of oil drops into the air-water surface. In contrast, calcium carbonate, which was produced when the solutions contained sodium carbonate, did not exhibit an antifoam effect. Indeed, by reducing the amount of calcium available to form calcium oleate, it sometimes diminished the defoaming effect that would otherwise have occurred. The foam stability results were compared with calculated values of entry, spreading and bridging coefficients.