Calculations for maximum volume fraction (phi(m)) for a monomodal and a bimodal dispersion are given. These are extended to express the volume fraction of dispersed phase (phi < phi(m)) for a bimodal distribution. By substituting the volume fraction, so obtained, various semiempirical laws relating relative viscosity to the volume fraction of the dispersed phase for monomodal dispersions can be extended to bimodal dispersions also. It was mathematically shown that the viscosity of a bimodal dispersion shows a minimum for a particular size ratio of small to large particles for a given relative number concentrations of small to large particles and the interspacing between the small and the large particles. Also, it was shown that an increase in the relative number concentrations of small to large particles, keeping the size ratio of small to large particles and the interspacing between the small and the large particles constant, always increases viscosity. These findings also have practical significance because they can be used to obtain high solid content dispersions with minimum viscosity. Candidate recipe and operating variables that can be varied to obtain either bimodal or very broad distributions through miniemulsion polymerization are finally identified. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 49-61, 2009