The use of axial-flow impellers in the up-pumping mode has been increasing, but little performance and design information is available. Up-pumping pitched-blade and high-efficiency impellers have been studied in solids suspension applications, and their performance has been compared to and contrasted with that of the more conventional down-pumping mode. Just-suspended speed data has been interpreted in terms of two literature correlations that can be used for design purposes. Just-suspended torque and power requirements are presented, as well as turbulent power number and flow pattern data. In general, the just-suspended torque and power requirements of up-pumping pitched-blade and high-efficiency impellers are substantially higher than those of the down-pumping mode. However, if a large impeller diameter is required to avoid critical speed limitations or to achieve sufficient power inputs at high solids loadings, then up-pumping impellers may be a viable option.