The rheology of aqueous dispersions of colloidal hematite (alpha-Fe2O3) rods with well-characterized shape and dimension was investigated. The effects of volume fraction (phi), aspect ratio, and Debye length (kappa(0)(-1)) on the rheology were studied in particular. ?he 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 zeta potential, which was characterized in the Smoluchowski limit. Their rheology was compared to that of spherical hematite prepared by the method of Matijevic (1985). Dilute solution viscometry indicated that the effects of kappa(0)(-1) and the aspect ratio on the O(phi(2)) 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 [Krieger and Dougherty (1959)]. The volume fraction dependence of the zero-shear viscosity eta(0) was found to be a strong function of both the aspect ratio and kappa(0)(-1). The aspect ratio affected both the volume fraction at which eta(0) diverged (phi(m)), and the strength of the singular behavior [characterized by alpha in eta(0) /mu = (1 - phi/phi(m))(-alpha)]. In contrast, kappa(0)(-1) affected phi(m), but not alpha. The effect of the aspect ratio and volume fraction on the linear viscoelasticity of suspensions for phi > phi(m) was quantified. The results highlight the particular ways in which the colloidal suspension rheology of moderate aspect ratio rods differs from that of spheres.