In this paper the kinetics of the formation of nanoparticles in microemulsions is studied by Monte Carlo computer simulation. It is observed that compartmentalization of the reactants induces a separation of the nucleation and growth processes, which is more clearly observed when the concentration of reactants is relatively high. It is also observed that growth by autocatalysis and by ripening overlaps at low concentrations but occurs on different time scales at high concentration. A comparison between the results of these simulations and those from Smoluchowski’s rapid-coagulation mechanism is made, showing that this theory is adequate to model the kinetics of these reactions.