The rheological behavior of dense, polymodal slurries is analyzed theoretically assuming the slurry is bimodal, composed of two relatively distinct particle fractions - a coarse fraction and a smaller fine fraction. The theory is applied to six commercial dense coal-water slurries. Comparison of the theory with reported measured viscosities supports the idea that these slurries behave bimodally. Data from experiments run with coal to separately specify the contributions of the colloidal and coarse particles to the measured viscosity show the behavior of the large particles to be independent of the shear rate and the slurries to behave bimodally.