The utilization of the laser-Doppler velocimetry technique in concentrated suspensions facilitated a direct measurement of particle migration velocities. Velocity measurements of dispersions at moderate and high particle concentrations, in the range of 0.3 < phi(s) < 0.50, showed a direct connection between particle lateral migration and changes in suspension velocity profiles. The longitudinal profiles lose their Newtonian shape at high concentrations. A qualitative agreement is shown in this work between the measured lateral and longitudinal velocity profiles and model calculations based on a phenomenological model.