The present paper deals with a comparative study of different theoretical models for evaluating shear capacity of external beam-column joints in RC structures. After a short overview of various models available in the scientific literature, a comparative analysis is presented. A wide experimental database has been collected for assessing the accuracy of the various models on a number of experimental results generally wider than those originally utilized by the authors. Finally, further calibrations of those models is presented along with the estimation of the relevant variability factor to be possibly utilized in seismic reliability evaluation of RC structures.