We derive new, exact series expansions for the effective elastic tenso
r of anisotropic, d-dimensional, two-phase disordered composites whose
nth-order tensor Coefficients are integrals involving n-point correla
tion functions that characterize the structure. These series expansion
s, valid for any structure, perturb about certain optimal dispersions.
Third-order truncation of the expansions results in formulas for the
elastic moduli of isotropic dispersions that are in very good agreemen
t with benchmark data, always lie within rigorous bounds, and are supe
rior to popular self-consistent approximations.