The standard (p(o) = 0.1 MPa) molar enthalpy of combustion of 4-iodobenzoic acid, at T = 298.15 K, was measured by static-bomb and rotating-bomb calorimetry, from which the standard molar enthalpy of formation, in the crystalline state, was derived. [GRAPHICS] The values obtained confirm that 4-iodobenzoic acid is a satisfactory test substance for combustion of organo-iodine compounds. Using a literature value for its standard molar enthalpy of sublimation, the standard molar enthalpy of formation, in the gaseous state, was also derived and compared with an estimate by means of structural contributions.