An approach to define collisional properties and kinetic coefficients for simulating multiphase flows with reactions by integrating discrete and continuum models is developed. Accordingly, the microprocesses are investigated separately by numerical simulations of a discrete system in order to obtain information about collision frequencies, diffusion rates, etc., and then this information is incorporated into a continuous population balance model. The approach is demonstrated on a two-phase turbulent flow in a pipe type reactor where a single irreversible coalescence reaction between the identical species of the dispersed phase takes place and on diffusion of droplets in a turbulent field. A generalization of the approach to a polydispersed system of species is outlined. (C) 2004 Elsevier Ltd. All rights reserved.