The effects of tetraalkylammonium ions on the stability of dilute o/w emulsions were investigated with turbidimetric measurements. Large tetraalkylammonium ions were found to induce flocculation of emulsions stabilized by ionic emulsifiers at ten times lower concentrations compared to divalent cations. Emulsions stabilized by nonionic surfactants were also destabilized by low concentrations of organic ions. Increasing the effective size of sodium ions by inclusion complex formation with a crown ether, was also found to destabilize the emulsion. All these observations demonstrate the importance of the ion size/hydrophobicity on the stability of emulsions in the presence of electrolyte.