The dependence of phase structure on the intensity of mixing was studied for two modified polyamide/[poly(phenylene oxide) + polystyrene] (50/50) blends with different viscosity ratios of components. In these blends, polyamide forms the matrix and the mixture of miscible polymers [poly(phenylene oxide) and polystyrene] forms the disperse phase at all rates of mixing. The average size of the droplets of the disperse phase grows with increasing rate of mixing. This (rather surprising) result is explained as a consequence of the dynamic equilibrium between breakup and coalescence of droplets in a highly concentrated system at the condition of steady mixing. Generally, the dependence of droplet size on rate of mixing is not necessarily a monotonic function for blends with a high content of the disperse phase. © 1993 John Wiley & Sons, Inc.