The effects of dye-polymer interactions on the T-g of dye-polymer blends have been investigated using a disazothiophene dye solute in a variety of polymer structures. The dye was found to decrease the T-g of some polymers (plasticization) while increasing the T-g of others (antiplasticization). The T-g of a dye-polymer blend depended on the polymer T-g, the dye solute T-g, their relative concentrations and dye-polymer affinity. Increasing dye-polymer affinity produced stronger interaction between the dye and polymer, leading to higher T-g of the dye-polymer blend. Excellent correlations were established between T-g enhancement and the dye-polymer solubility parameter match which was used to predict dye-polymer affinity. Solubility parameters indicated that the combination of polar and hydrogen bonding forces controlled the elevation of T-g, since the best correlation was obtained by neglecting dispersion forces.