Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling. A better method compared to expensive and time-consuming heating is desirable to accelerate the liquefaction and retard the crystallization process in honey. In this work, samples of crystallized honey were liquefied by an ultrasonic bath of 40 kHz at temperatures of 40-60 degrees C for 20,40 and 60 min. Then, the theological properties and crystal content were analyzed and compared to only heat-treated samples. Results show that an ultrasound treatment speeds up the liquefaction of honey especially at temperatures below 50 degrees C. Lower temperatures preserve the honey's quality and save the energy consumption. In addition, ultrasound-treated samples are clearer and more transparent than only heat-treated honey samples. The amount and size of the crystals were also smallest in the ultrasound treated samples. (C) 2011 Elsevier Ltd. All rights reserved.