During the last two decades, active research has gone into the theoretical and the practical aspects of the electro-mechanical impedance (EMI) technique for structural health monitoring (SHM). This paper reviews the theoretical developments in modelling the force transfer mechanism between the piezoelectric-ceramic (PZT) patch and the host structure pertinent to the EMI technique. The review covers the modelling efforts spanning about last one and a half decades. The models reviewed include the shear lag based model, simplified shear lag model, the refined shear lag model and the continuum shear lag model. The first three listed models ignored the inertia term. The last model, that is the continuum based model, takes care of all the piezo, structural and adhesive effects rigorously and simultaneously. Typical comparisons between the outcomes resulting from the models are discussed. © (2013) Trans Tech Publications.