The present work aims at an indepth investigation of the flow characteristics of gas-liquid two-phase flow through an undulated pipeline consisting of interconnected horizontal, upward and downward inclined sections. The conductivity probe technique has been adopted for this purpose. The experiments have been performed for phase velocities ranging from 0.28 m/s to 1.12 m/s for air and from 0.01 m/s to 1.12 m/s for water. Six parallel wire type conductivity probes have been installed in the upstream, uphill, downhill and downstream sections of the pipeline. Different methods of signal analysis namely the probability density function analysis and the Fast Fourier Transform are used. The slug characteristics in the different sections of the undulated pipeline are estimated using the cross correlation technique. The auto correlation function and photographic techniques provide an insight into the nature of slug dissipation in the downhill section. Further attempts have been made to estimate the slug velocity and slug length distribution in the downstream section using the random probe signals. (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.