Hybrid inorganic-organic composites, (K/Na)ZrSi(R)O-x, were synthesized from the hydrolysis of the mixture of zirconium n-propoxide (Zr(OPrn)(4)) and 3-glycidyloxypropyltrimethoxy silane (GPTS) in 1:1 mol ratio. The hydrolysis reaction was carried out with 0.1 molar HCl in 150 ml of butanol. Then, the synthesized Zr(OPrn)(4)-GPTS-hydrolyzate reacted with KOBut and NaOSiMe3 in 1:1 mol ratio at 40 and 50 A degrees C for 24 h, respectively. After these stages, composites were washed and dried under vacuum. Composites and their oxide prepared at 1250 A degrees C by calcinations were characterized by a combination of powder X-ray diffraction, scanning electron microscope, energy dispersive X-ray, Brunauer-Emmett-Teller analysis, Barrett-Joyner-Halenda analysis, and Fourier transform infrared spectroscopies. These hybrid inorganic-organic composites except oxides were used as catalysts in order to see their activities in the polymerization of epsilon-caprolactone (epsilon-CL). This study showed that new composite materials except their oxides were effective catalyst in epsilon-CL polymerization.