An experimental study of the structure of an acoustically forced, reacting two-phase jet was performed. The jet was acoustically forced to control the formation and evolution of large-scale structures in the near field of the jet. Phase-locked data acquisition techniques were used to correlate droplet statistics and dynamics with features of the large-scale structures. Phase Doppler interferometry was used to acquire droplet statistics. Planar imaging techniques were applied to document the distribution of droplets within the jet. The results show that the interaction between droplets and large-scale structures leads to a nonuniform distribution of droplets in the reacting jet. The combination of transport effects and droplet evaporation leads to the formation of droplet clusters. The group combustion behavior of the droplet field was evaluated by estimating the group combustion number from experimental data. External sheath burning is present in the early portion of the flame followed by a transition to external group combustion as clusters begin to be the dominant feature. Late in the cluster lifetime there is a shift to internal group combustion. (C) 2000 by The Combustion Institute.