The standard (p degrees = 0.1 MPa) molar enthalpies of combustion in oxygen at T = 298.15 K of three branched alkyl chain carboxylic acids, 2-methylpropanoic, 2,2-dimethylpropanoic, and 3-methylbutanoic, were measured by static bomb combustion calorimetry, from which their standard molar enthalpies of formation were derived. [GRAPHICS] The standard molar enthalpies of formation at T = 298.15 K of the gaseous carboxylic acids were derived using literature values of their standard molar enthalpies of sublimation or vaporization.