In an attempt to extend the applications of IR spectroscopy, we report here on a novel method for the determination of the tensile strength (Ts) of polybutadiene rubber (PBR). A simple linear correlation between Ts and the peak absorbance ratio was developed. The method is simple, direct, and fast and involves only the measurement of the absorbance ratio from the IR spectrum of PBR film. The results obtained by this (IR-based) method and the currently used (ASTM) method, for quality control/quality assurance purposes, were in good agreement.