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Velocity field was measured by laser Doppler UL + velocimetry in isothermal, turbulent bubbly gas-liquid flow through a 26.6 mm inner diameter vertical pipe. The measure-u, ments were made about 33 diameters downstream from the u~ pipe entrance, gas injection being just upstream of the enu~ trance. The gas phase radial distribution at the measurement VL plane exhibited influence of the injection device in that higher v~ gas fraction existed in the central region of the pipe. For (~V)L comparison, velocity field was also measured in isothermal, turbulent single-phase liquid flow through the same pipe at the same axial plane. Measured were the radial distributions of T~, liquid mean axial and radial velocities, axial and radial turx bulent intensities, and axial Reynolds shear stress. The radial y distributions of gas bubble mean axial velocity and axial velo-y+ city fluctuation intensity were also measured by LDV. A dualsensor fiberoptic probe was used at the same time to measure the radial distributions of gas fraction, bubble mean axial velocity and size slightly downstream of the LDV measurement plane. List of Symbolsf,f~ kL Fi'I G , Yh L R r; R* Re L v~ uL ULoan average gas bubble diameter friction factor, friction factor for gas-liquid flow liquid turbulent kinetic energy gas, liquid mass flow rate inner radius of pipe radial coordinate; nondimensional radial coordinate ( = r/R) liquid Reynolds number mean axial velocity of gas bubble mean axial velocity of liquid mean axial velocity for flow at the total mass velocity with properties of the liquid phase