The stability of macroemulsions formed upon mixing the phases of the Winsor III equilibrium was studied. The resulting macroemulsions contained the upper and lower phases, emulsified in each other; the middle phase did not coemulsify with them and separated within the first hour after emulsification. Within ca. 0.2 degrees C on the both sides of the balanced point, the macroemulsions were very unstable. Within the following 0.15 degrees C, a spectacular increase in stability by 3 orders of magnitude occurred on either side of the phase inversion temperature. The same pattern of macroemulsion stability was reproduced by varying salinity at constant temperature. The experimental data are in good agreement with a model, relating the rate of coalescence to the free energy penalty of hole nucleation in the emulsion films.(1)