Lamb wave analyses have been conducted on metallic and composite structures. The dispersion characteristics for these plate structures are evaluated using the Rayleigh-Lamb equations and an assumption that the material properties are known. In most studies, the elastic moduli used are determined using standard tensile tests. These properties have been used to adequately model the dispersive behavior of Lamb wave in metallic plates. It has been shown that the use of elastic properties from tensile tests is able to model the dispersive Lamb wave behavior. However, this may not be the case for plates made from woven fibre reinforced plastics. The effects of material properties on the propagation of Lamb wave in fibre reinforced composite plates are significant. In most of these investigations, the elastic properties used are obtained from tensile tests. It will be shown that the use of such properties will lead to significant inaccuracy in the determination of the dispersion characteristics of a composite plate.