The enthalpy of oxidation of La(B1-xB'(x))O3-delta (x = 0.25 and 0.75 for BB' FeCo, MnCo, MnNi and x = 0.2 for BB' CoCu) has been derived using solid solution models to analyse thermogravimetric measurements of oxygen non-stoichiometry vs. log(pO(2)) at 1273 K. For selected samples the enthalpy of oxidation has also been measured by TG-DSC, and the direct heat measurements agree well with the results from the solution models. The affinity for oxygen decreases when x in La(B1-xB'(x))O3-delta increases from 0.25 to 0.75. This trend may be extended to a larger range of x-values (x is an element of[0,1]) when isotherms from the literature are included in the solution modelling. For the materials investigated in this work, the affinity for oxygen decreases in the order Mn0.75Ni0.25 > Mn0.75Co0.25 > Fe0.75Co0.25 (for x = 0.25) and in the order Mn0.25Co0.75 > Fe0.25Co0.75 > Mn0.25Ni0.75 (for x = 0.75). The Co0.80Cu0.20 containing material has the smallest affinity for oxygen among all the samples. (C) 2010 Elsevier B.V. All rights reserved.