The standard (p(0)=0.1 MPa) molar enthalpies of formation Delta(f)H(m)(0) (1) at the temperature T=298.15 K were measured using combustion calorimetry for 1,3-di-iso-propylbenzene, 1,4-di-iso-propylbenzene, and 1,3,5-tri-iso-propylbenzene. The standard molar enthalpies of vaporization Delta(1)(g)H(m)(0) of these compounds were obtained from the temperature function of the vapour pressure measured in a flow system. Values of the small (1-2 kJ mol(-1)) stabilized interactions of iso-propyl substituents were derived from the enthalpies of formation in the gas phase of the iso-propylbenzenes studied.