Thermodynamic parameters for thermal denaturation of β-lactoglobulin (β-lg) should account for the dissociation coupled unfolding (DCU) transitions, Dimer Monomer Unfolded state. Purified β-lg (0.4-4mgml - 1 in 50mM glycine-glycine-HCl buffer, pH 2.6) was heated and monitored by UV-difference spectrophotometry. The Monomer Unfolded state transition occurred at 65-95 o C with T m equal to 82 o C and a Gibbs free energy change (ΔG U 0 ) of 51kJmol - 1 . Such results were combined with parameters for β-lg dissociation leading to the Gibbs free energy change for DCU (ΔG D C U 0 ) of 128 (+/-8.3)kJmol - 1 . The enthalpy and entropy change for DCU was (ΔH D C U 0 ) equal to 373kJmol - 1 and (ΔH D C U 0 ) 824Jmol - 1 K - 1 . Thus, the room temperature stability of β-lg is 76kJmol - 1 higher than reported previously. The possible significance of such results for protein stability function relations (PSFR) is discussed.