The dispersion relations of oscillation modes in a piezoelectric slab with hexagonal symmetry are given, considering the slab infinite with respect to the axesx1andx2with the six-order symmetry axis perpendicular to thex1–x2plane. Four types of modes are identified: two of them are transversal horizontal and the other two are associated to electrostatic potential waves which determine the longitudinal and flexural modes. The secular equations for these modes are given and numerical results for the piezoelectric transducer ceramic slab are obtained and compared to experimental results with a very good agreement. ©1997 American Institute of Physics.