A variety of LDV experiments were conducted to assess the influence of solids loading, Reynolds number and particle size distribution on velocity fluctuations and flow behavior in fluid-particle pipeline systems. This talk will summarize these experimental findings and those of other researchers. In addition, detailed comparisons of experimental results for the mean and fluctuating velocity of both phases with multiphase CFD model predictions will be presented. These comparisons indicate the flow regimes where models that utilize concepts from kinetic theory to describe particle velocity fluctuations are successful and where these models fall short.