Increased use of instrumental analysis techniques is being required for critical quality control of polymeric raw materials used in the Thermal Protection System of Space Shuttl's External Fuel Tank. This paper is concerned with the FTIR evaluation of commercial room temperature vulcanized silicones. These silicone materials are two-component systems and the methodology developed is a comparison technique, and is performed via a computerized difference spectroscopy approach. A reference material is used as standard, and the subsequent lots are compared with the standard to assess their acceptability and conformance to specificatio. Results obtained so far indicated that the FTIR technique is a viable quality control procedure for use as a routine receiving/acceptance test.