Concrete elements such as slabs, footings and some types of beams are usually designed without web reinforcement, meaning that the shear force must be resisted by concrete only. However, current design provisions such as ACI, Eurocode 2 and CSA use sectional methods to assess the shear strength of such elements. Such methods are empirical or semi-empirical at best, and thus, in certain situations, they may lead to an inaccurate assessment of the shear strength. In this paper, a compression field based model to assess the shear strength of concrete slender beams was proposed. The proposed model is less dependent on the empirical approach than other existing models, which gives it an advantage when assessing unconventional cases. The accuracy of the proposed model as well as ACI, Eurocode 2 and CSA models to predict the shear strength was validated using a data base of 479 specimens collected from literature. The proposed model has proven to yield accurate and consistent results in comparison with ACI, Eurocode 2 and CSA sectional models. Furthermore, the proposed model has shown that the effective depth of the beam has either very little or no influence on the shear strength. Finally, a parametric study was also conducted to study the influence of the various parameters on the shear strength.