The standard (p(o) = 0,1 MPa) molar enthalpies of combustion in oxygen, at T = 298.15 K, were measured by rotative bomb calorimetry for crystalline N,N-diethyl-N'-furoylthiourea, (2-C4H3O)CONHCSN(C2H5)(2), HFET, and N,N-diisobutyl-N'-furoylthiourea, (2-C4H3O)CONHCSN(iso-C4H9)(2), HFIB. The standard molar enthalpies of sublimation of both HFET and HFIB were measured by high-temperature Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds, in their crystalline and gaseous phases. [GRAPHICS]