Transition from bubbling to turbulent in a conventional gas-solid fluidized bed was evaluated from trajectory of particles in fluidized bed. A series of experiments were carried out in a lab-scale fluidization bed using radioactive particle tracking (RPT) technique for recording the position of a tracer in the bed. Statistical parameters, such as standard deviation and skewness of the time-position data, were utilized to determine the transition velocity from bubbling to turbulent regime. The results showed that the data obtained by the RPT technique can predict transition velocity. It was shown I hat the standard deviation of position fluctuations reach a maximum with increasing superficial gas velocity corresponding to regime transition. It was shown that transition from bubbling to turbulent car be determined using skewness and kurtosis of time-position data. The velocities obtained in this work are in good agreement with the available correlations. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.