In relation to the development of the interfacial area transport equation, this study was aiming at collecting accurate data sets on axial developments of local flow parameters such as void fraction, interfacial area concentration, and gas velocity. The local flow measurements of air-water bubbly flow in a vertical 9-min-diameter tube were performed by means of a stereo image-processing method. A total of three data sets were acquired consisting of two gas flow rates, 0.013-0.052 m/s, and two liquid flow rates, 0.58-1.0 m/s at six axial locations. The data would be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. (C) 2003 Elsevier Science Ltd. All rights reserved.