This paper presents an 18-node assumed strain solid element with mechanical-piezoelectric coupling. In the formulation, electric potential is regarded as a nodal degree of freedom in addition to three translations at each grid point. Since the assumed strain solid element is free of locking, the element can be used to analyze behavior of very thin actuators without locking. Using the solid element, we have analyzed the actuation performance of a composite multi-layered piezoceramic actuator and compared the result with measured data. The numerical estimation agreed well with the measured displacement for simply supported boundary condition and for low input voltage. (C) 2002 Elsevier Science B.V. All rights reserved.