The irreversible thermal denaturation of lentil lectin was investigated at pH 7.4 using different techniques including high-sensitivity differential scanning calorimetry, differential detergent solubility thermal gel analysis, intrinsic fluorescence and hemagglutinating activity assays. The shape of the transition, as well as its scan-rate dependence, can be explained by assuming that thermal denaturation takes place according to the kinetic scheme N k-->D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation, N the native state, and D the denatured one. On the basis of this model, the value of the rate constant as a function of temperature and the activation energy were calculated. The analytical data obtained with the other methods used in this work support the proposed two-state kinetic model.