The hybrids prepared from polydimethylsiloxane ( PDMS) and tetraethoxysilane ( TEOS) have been well known to be rubbery hybrid materials. In this report, the authors have investigated the electrical insulating and heat resistive properties of the hybrids by changing the molar ratio of TEOS to PDMS. The electrical insulating properties are evaluated by volume resistivity and AC breakdown strength at room temperature. The resistivity is about 10(13) Omega.m and AC breakdown strength is about 25 kV/mm irrespective of the molar ratio. Heat-resistive properties are evaluated by the weight loss after keeping for 480h at 200 degrees C in air. The weight loss becomes smaller as the TEOS content increases, and it is less than 3%. It has been clarified that the hybrids have good electrical insulating and heat- resistive properties.