In the past decade, the interest in phase change materials (PCMs) has grown significantly due to their ability to store large amounts of thermal energy in relatively small temperature intervals. Accurate knowledge of thermo-physical properties is a prerequisite for any reliable utilization of these materials. The T-history method is widely used for the investigation of PCM. This paper presents an improved measurement technique for the characterization of PCM using the T-history method. The suggested improvements include the arrangements made in three different prospects: the experimental setup, data processing and data representation. T-history measurements of organic RT21 and inorganic SP22 A17 (RUBITHERM (R) GmbH) PCM were performed. The applied arrangements resulted in the temperature accuracy of +/- 0.3 degrees C and the reduction of uncertainty associated with heat stored/released between the cooling and heating measurements. The obtained results showed some important aspects of the T-history PCM investigation and could provide more effective design and development process of the thermal energy storage systems based on the investigated materials. (c) 2013 Elsevier Ltd. All rights reserved.