New flexible hybrid materials had been synthesized successfully by incorporating ethylene-propylene nonconjugated diene terpolymer (EPDM-ENB), which had been functionalized with S-aminopropyl trimethoxysilane (APS), with highly reactive tetrabutyl titanate and tetraethoxysilane. The materials with low inorganic content displayed high transparency due to the formation of covalent bonds between the polymer chains and the inorganic network in the hybrids. The titanium systems were found to be more compatible than the corresponding silica hybrid materials of equal alkoxide content. As the inorganic content increased, the dynamic tensile modulus of the hybrid showed significant improvement over pure EPDM-ENB in the region above T-g of EPDM-ENB. For the EPDM-ENB/TiO2 hybrids, when the total metal alkoxide content is fixed, the properties of the hybrids were not affected by partial replacement of tetrabutyl titanate with tetraethoxysilane.