Possible influence of experimental nonequilibrium conditions on heat denaturation and renaturation of biopolymers has been studied. The analysis has been made using a standard kinetic model of transition between two states. Regularities are revealed which determine the position and shape of the heat absorption peak in calorimetric experiments on direct and reverse scanning (heating and cooling). The evaluation formulas for obtaining kinetic information from such experiments are given and their application is discussed. The results obtained can be useful in analysis of real calorimetric curves. It is shown that upon heating and cooling in nonequilibrium conditions the behavior of the system can differ qualitatively. The above difference takes place when the renaturation rate decreases on lowering the temperature. In this case, heating under nonequilibrium conditions leads only to a shift of denaturation transition to the higher temperatures while nonequilibrium cooling may result in complete or partial irreversibility.