Asphaltenes fractionated from Hondo Crude Oil (a heavy crude from off-shore California) were dissolved in mixtures of toluene and heptane to create model oils. The emulsion stability of water-in-model oils was investigated over a range of pH. High pH (around 12) gave rise to water-in- oil emulsions with very high stability. However, the addition of 5-ß -Cholanic Acid (ß -CA), a carboxylic acid very similar to naphthenic acids found in petroleum fluids, to the model oil reduced dramatically the emulsion stability. This effect was more significant at higher pH (pH 12). Moreover, the amount of ß -CA that destabilized the water-in-oil emulsion at pH 12 was around 500 ppm. These results suggested that the presence of ß -Cholanic Acid or other naphthenic acids with similar structure could prevent the formation of stable W/O emulsions. With this in mind, water-in-petroleum emulsions were prepared in order to study the addition of ß -CA to different whole crude oils and evaluate the stability of the emulsion formed at high pH. The results from the later study were very satisfactory and demonstrate that carboxylic acids with a similar molecular structure to ß -CA (that is, a carboxylic acid for which its hydrophobic moiety is largely aliphatic) could break asphaltenic-film-stabilized emulsions.