Silicone epoxy (SiE) resins were synthesized through the hydrolytic condensation of 2-(3,4-epoxycyclohexylethyl) methyldiethoxysilane (EMDS) and the cohydrolytic condensation of EMDS with dimethyldiethoxysilane. Structural characterization was carried out by H-1-NMR, Si-29-NMR, and mass spectrometry analysis; the resins were linear oligomers bearing different numbers of pendant epoxy groups, and the average number of repeat Si-O units ranged from 6 to 11. Methyhexahydrophthalic anhydride was used to cure the SiE resins to give glassy materials with high optical clarity. The cured SiE resins showed better thermal stability and higher thermal and UV resistances than a commercial light-emitting diode package material (an epoxy resin named CEL-2021P). The effect of the epoxy value on the thermal and mechanical properties and the thermal and UV aging performances of the cured SiE resins were investigated. The SiE resins became more flexible with decreasing epoxy value, and the resin with the moderate epoxy value had the highest thermal and UV resistances. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1216-1224, 2011