[en] Additional problems for the treatment of heavy particle dispersion arise from the effect of crossing trajectories. This effect is caused by an external potential force field acting on the particle and producing the drift velocity between the particle and the fluid. As a result particle crosses the fluid turbulence eddies and loses velocity correlation more rapidly than a fluid point. The heavy particle integral time scale and consequently the dispersion coefficient decreases. Similar effect arises in nonhomogeneous flows when particle migrates from regions of different velocities, but in that case the problem is even more complex because of the different particle velocity fluctuations in two regions. The aim of this study was to demonstrate these effects in experimentally investigated dispersion situations of Snyder and Lumley (1971), Wells and Stock (1983) and Arnason (1982) by means of a comparison with a recently developed Lagrangian Stochastic-Deterministic (LSD) model (see Milojevic, 1986). The LSD model is stochastic in the sense that the 'instantaneous' fluid velocity field is generated from known turbulence energy and time scales of large eddies by using a random sampling. (orig./GL)