The variation of elastic moduli among five pyroxenes exhibiting three crystal structures is generally small. The variations that do exist are related to structural differences. C11 is most sensitive to compositional changes on the basis of a mechanical structural analog. Its small variation among these pyroxenes suggests that the compositional range reflected by these samples (enstatite, bronzite, diopside) does not affect the elastic moduli. C33 is most sensitive to structural perturbations. The large variation of C33 (20%) implies that the small variations in crystal structure dominate the variations in elastic moduli.