Theoretical and experimental investigations of the dynamics of aggregate aerosols have been conducted and led to the development of models to describe the kinetics of agglomeration. The agglomeration rate is determined by the mobilities of the agglomerate particles and by their collision cross sections. Agglomerate particles coagulate more rapidly than do dense particles due to their larger collision cross sections. Experimental studies have been conducted to explore a number of aspects of the evolution of aggregate aerosols. The structure-drag relationship has been explored by image analysis of transmission electron micrographs of mobility classified aggregate particles. Structural rearrangements during sintering of aggregates have been explored by heat treating aggregate particles while they are still entrained in the carrier gas. Particles are observed to retain the appearance of fractal clusters of smaller primary particles throughout coalescence that leads to many primary particles from the original particle being incorporated into a single primary particle in the sintered agglomerate. This observation raises serious questions about the inference of mechanisms of particle growth from structure measurements alone.