This paper investigates the use of the shear vane technique as a means of determining frictional and cohesive interparticle force contributions to the shear strength of coarse glass bead powders and slurries. To this end, the shear strength of 203-mu m glass beads in air and slurried in water and kaolinite suspensions was determined as a function of vane immersion depth, vane geometry, and container size. Both vane immersion depth and container diameter are found to significantly impact the shear strength measured using the vane technique. An equation describing interparticle frictional and cohesive contributions to shear vane measurements was derived in an effort to describe the experimental results. A Janssen stress distribution model for granular materials forms the basis for this equation and appears to explain the behavior of shear strength measurements at varying immersion depths. The presence of the Janssen stress distribution can affect the interpretation of shear vane results. Rather than shear strength being a material property, as is the case with flocculated colloid slurries and polymer solutions, shear strength becomes a process property where vane depth, container size, and container material can result in significant measurement variations. Such parameters should be considered before using the shear vane results on applications involving granular material components.