The uniaxial stress‐strain behavior of highly filled elastomers is examined in terms of a simplified thermodynamic model. Experimental data are presented showing the stress‐strain‐dilatational behavior at a series of hydrostatic pressures from which the behavior at constant volume can be obtained. Deviations from this constant volume stress‐strain state are shown to be dependent upon the rate at which pressure‐volume and surface energies are being expended by the material due to the formation and growth of vacuoles. Mathematically and experimentally the behavior is considered to be essentially reversible as experimental data indicates. Therefore, the only forms of energy considered are mechanical, and energy balances are made using only force‐deflection, pressure‐volume, and surface energies. This method of approach accounts for the energy sinks which reduce the rate at which the material accumulates mechanical energy and indicates what factors govern the stress‐strain response.