Gas-liquid slug flow in a downward inclined pipe was studied experimentally by employing a wire-mesh sensor that enables quantitative measurements of the cross-sectional void fraction distribution. Processing of the wire-mesh sensor data was applied to carry out a statistical analysis of characteristic parameters of downward slug flow, such as bubble and liquid slug length distributions, as well as to determine the ensemble-averaged shapes of the bubble nose, liquid film and bubble tail. It was found that the pipe inclination affects mainly the bubble length, while variation in the gas flow rate affects both bubble and slug length. The bubble nose shape is more sensitive to the flow conditions than the bubble tail. The 3D structure of an elongated bubble in downward slug flow was reconstructed from the wire-mesh sensor data. (c) 2008 Elsevier Ltd. All rights reserved.