In this paper a 4-unknown quasi-3D shear deformation theory for the static analysis of advanced composite plates is presented. The beauty of this theory is that, in addition to including the thickness stretching effect (ezz≠. 0), the displacement field is modeled with only 4 unknowns, which is even less than the first order shear deformation theory (FSDT). The principle of virtual work is employed to derive the governing equations and boundary conditions. Results from this theory are compared with the CPT, FSDT, and other quasi-3D HSDTs. As conclusion, this theory is as accurate as other quasi-3D HSDTs with higher number of unknowns and so it becomes more attractive due to smaller number of unknowns. © 2013 Elsevier Ltd.