This paper describes an investigation of liquid lump velocities in vertical upward gas-liquid two-phase flow. Velocities of individual liquid lumps, such as liquid slugs, huge waves, disturbance waves or ephemeral large wave are determined by a computer-aided data-processing method ; that is time-varying cross-sectional mean liquid holdups are electrically detected at two axially separated locations of the tube, and each liquid lumps from the two holdup signals recorded on magnetic tape. It is demonstrated how the mean values of liquid lump velocity and its standard deviations depend on the gas and liquid flow rates and the related flow patterns. Furthermore, histograms of liquid lump velocity and the statistical relation between wave height and velocity are presented.