The dependence of the surfactant solubility temperature on the micellar solution concentration is analyzed on the basis of strict thermodynamic relationships and using the ideal monodispersed micellar solution model. The approach is illustrated in application to theN-dodecanoyl-N-methylglucamine-water system. Experimental measurements of the surfactant dissolution temperatures and heats have been performed for the system under study by the differential scanning calorimetry (DSC) method. The calculated temperature change along the Krafft boundary is in reasonable agreement with the experiment. Problems of the DSC data treatment for the phase transition of interest are discussed.