Two NMR velocity imaging methods based on the pulsed field gradient stimulated-echo technique are evaluated for the measurement of fluid flow in porous media. The spatial resolution and dynamic scale of velocity imaging experiments are chosen to represent the macroscopic behavior of the complex motion of fluid molecules. A theoretical formulation for data interpretation is presented and demonstrated with experimental data for water flow in a glass-bead pack and sandstone samples. Velocity imaging methods investigated include the use of flow-induced phase shifts and the measurement of spatially resolved velocity distributions. The results show that the phase-shift method is not suitable for some porous media. By contrast, the measurement of spatially resolved velocity distributions not only allows a map of mean velocity to be determined, but also provides information about the velocity field within each elemental volume of the image.