The objective of this study was to develop some new concepts of importance when trying to optimize the viscosity/modulus and impact relative to the particle-size distribution in suspensions and particulate composites. The results of this study appear to indicate that, conceptually, it is possible to significantly improve the viscosity versus the impact balance for material formulations by optimizing the particle-size distribution. For binary particle-size distributions, the influence of the preferred particle-size distribution, as determined using a square-root distribution, did not yield the most desirable particle-size distribution if the particle-to-particle component of the interaction coefficient was high. However, if three or more particles were utilized in the distribution, then the optimum particle-size distribution utilized can apparently be characterized using the square-root distribution even when the particle-particle component, up,, of the interaction coefficient, sigma, was found to be quite high. In addition, this same square-root particle-size distribution can also satisfactorily predict a probability of impact that can remain consistently high as long as the particles utilized are well chosen and not too close in size. Thus, this preferred particle-size distribution can be utilized to predict at least one of the preferred distributions to optimize the balance of properties between impact and the viscosity/modulus.