This paper is aimed at improving the current understanding of the mechanisms of shear transfer in interior beam-column joints of reinforced concrete frames. Simple variable-angle truss models are used to illustrate the joint shear transfer mechanisms. The model is used in the paper to evaluate the relative importance of those variables that are deemed to affect the shear strength of joints in the current New Zealand Concrete Structures Standard, (SNZ, 1995). The analyses suggest that some of the variables currently being considered might not be as important as thought and that the current design recommendations can be simplified and, in general, be eased. The authors propose a simple three-component equation for use in design. The design equation is based on the results of a parametric analysis and was calibrated against a database of tests obtained from the literature.