The rheology of aqueous dispersions of colloidal hematite(α-Fe2O3)rods with well-characterized shape and dimension was investigated. The effects of volume fraction (φ), aspect ratio, and Debye length(κ0−1)on the rheology were studied in particular. The particles were spindle-type bodies with aspect ratios equal to 8.4 and 4.8. They were dispersed in aqueous solutions of known ionic strength at a ζ potential, which was characterized in the Smoluchowski limit. Their rheology was compared to that of spherical hematite prepared by the method of Reference 1985. Dilute solution viscometry indicated that the effects ofκ0−1and the aspect ratio on theO(φ2)contribution to the low-shear effective viscosity were of comparable magnitude, and that the Huggins coefficient was a decreasing function of the aspect ratio. For concentrated suspensions, the dimensionless shear thinning was adequately fit by a correlation involving a critical stress, which was originally developed for spherical suspensions [Reference 1959]. The volume fraction dependence of the zero-shear viscosityη0was found to be a strong function of both the aspect ratio andκ0−1.The aspect ratio affected both the volume fraction at whichη0diverged(φm),and the strength of the singular behavior [characterized by α inη0/μ=(1−φ/φm)−α]. In contrast,κ0−1affectedφm,but not α. The effect of the aspect ratio and volume fraction on the linear viscoelasticity of suspensions forφ > φmwas quantified. The results highlight the particular ways in which the colloidal suspension rheology of moderate aspect ratio rods differs from that of spheres.