The governing equations for geometrically nonlinear, arbitrarily laminated rectangular plates reinforced by stiffeners which include piezoelectric and composite layers are presented. General equations obtained in the paper are reduced to a single equation of motion for piezoelectrically reinforced, geometrically linear, specially orthotropic plates. A criterion for an effective control of forced vibrations of such plates using piezoelectric stiffeners and a static electric field is illustrated. Active control of dynamic stability using a dynamic electric field with a frequency equal to that of the in-plane load is also considered. In addition, an approach to the analysis of piezoelectrically stiffened nonlinear plates whose motion is represented by single-term functions of the coordinates is discussed. Numerous active control problems can be addressed using the theory outlined in the paper. © 1993.