AbstractPresented here is new unified theory on particle motion in a turbulent dilute two‐phase suspension flow. Results of numerical calculations based on this theory have been found to agree closely with results of recent in‐situ local measurements of a two‐phase flow in a vertical pipe by the use of the non‐intrusive laser‐Doppler anemometry. In particular, a more plausible explanation is now provided for the measured peculiar migratory behaviors of particles in the region close to the