This paper discusses nine recent tests designed to investigate if current provisions for one-way shear in the ACI 318-05 Building Code are unconservative when applied to thick slabs or large, wide beams. The tests addressed the influence of member width and the presence of shrinkage and temperature reinforcement, which are two factors that may influence the shear capacity of slabs. Member width was observed to have no significant effect on the shear stress at failure for one-way slabs and for wide beams. The presence of shrinkage and temperature reinforcement also did not influence the one-way shear capacity. These findings indicate that ACI 318-05's provisions, which dictate different levels of useable shear capacity for slabs, wide beams and narrow beams, can result in inadequate levels of safety for both thick slabs and large wide beams. Because narrow design strips have been shown to behave in shear in a similar manner to wider members, the well-established size effect of decreasing shear stress at failure as the member depth increases also applies to wide beams and thick one-way slabs. The author recommends that ACI 318-05's basic expression for shear strength be reformulated to better predict the shear capacity of members regardless of depth or classification.