Inhibiting naphthenate salts that can form precipitates or emulsions during crude oil production or processing. An effective amount of a naphthenate inhibitor, such as a hydrotrope, is provided into the production fluids for contact with mixtures of oil and water in the formation, the production equipment, or processing systems. It is believed that the naphthenate inhibitors, such as monophosphate ester or diphosphate ester, exhibit surface-active properties that cause the inhibitors to align and concentrate in a layer at the oil-water interface and thereby prevent interactions between organic acids in the oil phase with cations or cation complexes in the water. It is believed that the physical positioning and geometry of the naphthenate inhibitor blocks the growth of naphthenate salt crystals. However, it is preferred that the naphthenate inhibitors also avoid the formation of oil-in-water and water-in-oil emulsions.