The temperature dependence of the plane-strain initiation fracture toughness (KJICi) is modeled micromechanically for a variety of advanced aluminum alloys that fail by microvoid processes. Materials include precipitation-hardened ingot metallurgy, spray formed, submicron-grain-size powder metallurgy, and metal-matrix composite alloys. A critical-plasticstrain-controlled model, employing tensile yield strength, elastic modulus, work hardening, and reduction of area measurements, successfully predicts KJICi versus temperature for eight alloys, providing a strong confirmation of this approach. Modeling shows that KJICi is controlled by the interplay between the temperature dependencies of the intrinsic failure locus εfp (σmσfl) and the crack-tip stress/strain fields governed by alloy flow properties. Uncertainties in εfp (σmσfl), as well as the critical distance (volume) for crack-tip damage evolution, hinder absolute predictions of KJICi. Critical distance (calculated from the model) correlates with the nearest-neighbor spacing of void-nucleating particles and with the extent of primary void growth determined from quantitative fractography. These correlations suggest a means to predict absolute plane-strain fracture toughness.