A comparison of calculated and measured glass transition temperatures of a series of three-component hydrocarbon blends was performed. The blends were prepared as mixtures of an elastomer with different proportions of tackifying resin and oil. Glass transition temperature, T-g, was measured by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) at four measurement frequencies. Most of these blends had pressure-sensitive adhesive (PSA) properties, and were used to prepare a series of PSA tapes. The adhesion of the PSA tapes was shown to be strongly dependent on T-g. Tack of PSA tapes was measured at two different temperatures, and shown to be directly correlated to the blend T-g. Several predictive methods for blend T-g that are based on individual component T(g)s were evaluated. The prediction of blend T-g is far more accurate if the individual component T-g values are determined by DMA instead of DSC. In addition, the Gordon-Taylor equation gave a significant improvement on predicted blend T-g when compared to the Fox equation.