Transition from coalescent to aggregate growth of soot particles in laminar premixed flames was investigated using detailed numerical simulations. A method-of-moments formulation for particle amregation was developed on the basis of recent Monte Carlo simulations and coupled with a detailed chemical kinetics mechanism of soot formation. The combined model was applied to ensemble-averaged simulations of a number of burner-stabilized premixed laminar flames and compared to measurements. The effect of initial conditions on the transition from coalescent to aggregate growth was investigated by simulating a series of freely propagating laminar premixed flames. The instant of transition and the degree of aggregation were analyzed in relation to variations in fuel type, fuel/air equivalence ratio, and pressure. The analysis demonstrated a complex interaction of particle nucleation, surface growth, and coagulation. with nucleation playing a key role in the transition from coalescent to aggregate growth. The present conclusions are in accord with the prior theoretical study. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.