The cavities of molecular sieves offer an opportunity for synthesis of periodically ordered semiconductor nanoclusters. Ge clusters were synthesized in zeolite Y by thermal decomposition of GeH4 absorbed in the zeolite cages. Upon inclusion of germanium in proton exchanged zeolite Y (HY), the X-ray diffraction (XRD) pattern shows a small change in line positions and considerable change in intensities. No extra reflections were detected in either XRD or transmission electron diffraction (TED) for the samples synthesized at 300 °C. These observations are in accordance with the energy dispersive X-ray (EDX) spectroscopy data which reveal the presence of germanium within the HY in concentrations higher than 5×1019 cm-3. At annealing temperatures higher than 500 °C, small Ge crystallites (approximately 0.2 μm) form on the exterior surface of the HY, as documented by TED, TEM and absorption spectroscopy. The results from the absorption and photoluminescence spectroscopy of the Ge loaded HY will be discussed.