Suspensions of nonspherical rigid particles in liquids are ubiquitous in many industries, such as printing and papermaking, petroleum, polymer, aerospace, bioengineering, construction, ceramics, coal, magnetic media, pharmaceutical, and food. Many polymeric composites are manufactured from suspensions of rodlike fibers in polymer melts. Fibers of rayon, vinylon, glass, nylon, and carbon materials are often utilized. In light of the practical applications just mentioned, a good understanding of the rheological behavior of particulate suspensions of nonspherical particles is important. The existence of steady-state rheological properties of a suspension implies that the suspension ultimately attains a unique steady-state orientation distribution, regardless of the initial orientation state of the particles. When a suspension consists of particles of different aspect ratios, the particles of the same suspension rotate with different periods of rotation, depending on the aspect ratio. As a consequence, the orientation distribution function is no longer periodic.