In high-velocity gas-particle flows with high mass loading of particles, the inertial and viscous effects are dominated by contributions from the particle phase. In a recent article (Dasgupta et al., AIChE J., 40 (1994) 251), we derived a mathematical model for the fully developed flow of such a suspension in a vertical pipe and showed that the non-uniform distribution of particles over the cross-section, seen experimentally in such flows, is a direct consequence of the unsteady fluctuations. In this article, we present performance diagrams predicted by this model over a wide range of operating conditions in the cocurrent upflow, countercurrent flow and cocurrent downflow regimes. Comparison of the model predictions with experimental data reveals good agreement in some cases and large departures for flows at the highest solids loadings.