An experimental study was conducted to investigate the heat transfer performance of a pulsating heat pipe (PHP) charged with deionized water and surfactant solution. The inner diameter of the PHP was 2 mm. The surfactant was sodium stearate, and the concentrations of sodium stearate solutions were 10, 20 and 40 ppm. The experimental results indicated that the heat transfer performance of the PHP was greatly influenced by the surfactant solution, and the influence was dependent on the charge ratio and the concentrations of the solutions. The PHP with 10 ppm sodium stearate solution showed better performance than the PHP with deionized water within the whole test range (0-160 W). Nevertheless, the enhancement effect of the heat transfer was apparent only when the heat flux was very high for the 40 ppm sodium stearate solution. Compared with the PHP with deionized water, the thermal resistance and the temperature difference between the evaporation section and condensation section could be decreased by 0.13 K/W and 20.8 K when the charge ratio, the heating power and the concentration of the solution was 58%, 160 W and 40 ppm, respectively. (C) 2014 Elsevier Ltd. All rights reserved.