In this paper, the relationship between fiber shape and relative viscosity of a fiber suspension is explored. A numerical simulation has been used to model non-Brownian curved rigid fibers in suspension under the influence of Newtonian shear flow. Curvature in the simulated fibers was taken to represent general deformities of real fibers in suspension. The simulation method was previously used by Joung et al. [J. Non-Newtonian Fluid Mech. 99 (200 1) 1] to determine suspension viscosity for flexible fibers in suspension. When compared to the equivalent straight rigid fiber suspension, fiber curvature was found to contribute to a large increase in suspension viscosity. For typical semi-concentrated to concentrated suspensions, curved fibers were observed to produce viscosity increases of the order twice that of straight fiber suspensions. Results indicate that even a small bend in the fibers may cause a large bulk viscosity increase, Suspension viscosity is therefore highly dependent on the quality control measures taken during sample preparation.