A power-law expression is proposed for correlating the temperature dependence of infinite-dilution activity coefficients (gamma(infinity)(ij)) for nonelectrolyte solute-solvent binary pairs and for pairs including an ionic liquid: ln gamma(infinity)(ij) (at T)/ln gamma(infinity)(ij)(at T-ref)= (T-ref /T)(theta ij), where theta(ij) = 0 for Lewis-Randall ideal solutions, theta(ij) = 1 for classic enthalpy-based Scatchard-Hildebrand regular solution and van Laar models, and -5 < theta(ij) < 5 for most real binaries. The exponent theta(ij) is a function of partial molar excess enthalpy ((h) over bar (E,infinity)(ij)) and entropy ((s) over bar (E,infinity)(ij)) such that theta(ij) 1 = 1/[1-T (s) over bar (E;infinity)(ij)/(h) over bar (E,infinity)(ij))]. Real binaries are classified into seven types corresponding to distinct domains of gamma(infinity)(ij) and theta(ij). The new method provides a framework for correlating phase-equilibrium driven temperature effects for a wide variety of chemical and environmental applications. (C) 2014 American Institute of Chemical Engineers AIChE J, 60: 3675-3690, 2014