Free vibrations of triangular and trapezoidal plates have been analysed recently theoretically and experimentally by many authors. Some of them applied the Rayleigh-Ritz procedure, while others proposed to use the Kantorovich-Vlasov method, reducing the problem to solution of an ordinary differential equation.In this note, the method developed in ref. 7 on the basis of Reissner’s modified variational theory is extended to include trapezoidal cantilever plates (Fig. 1).Comparison of theory and experiment shows that, retaining four terms in the deflection function, one obtains three natural frequencies to a high degree of accuracy.