Flow induced by an impeller in an unbaffled cylindrical tank was studied. In Part I, both mean and turbulent (root-mean-square) velocities in all three directions were measured using a laser Doppler anemometer (LDA). The effects of the impeller rotational speed and clearance to tank bottom on Bow characteristics were investigated. It is found that the Bow turbulence is approximately homogeneous in the bulk liquid except in the impeller stream. Near the gas-liquid interface the turbulence is strongly damped by the surface tension, and is fairly anisotropic. The mean and rms velocities in dimensionless form were observed to be independent of the impeller rotational speed. It was also found that the impeller clearance to the tank bottom affects the pumping capacity of the impeller, i.e. the rate of flow ejected by the impeller blades, but does not influence the circulation capacity of flow in a vertical plane.