The enthalpy of sublimation of diphenylacetylene at 298.15 K, DELTA(cr)g H(m)THETA (C2(C6H5)2] = 95.1 +/- 1.1 kJ mol-1, was derived from vapour pressure-temperature data, obtained with two different Knudsen effusion apparatus, and from heat capacity measurements obtained by differential scanning calorimetry. The molybdenum-diphenylacetylene bond dissociation enthalpy in Mo(eta5-C5H5)2[C2(C6H5)2] was reevaluated as 115 +/- 26 kJ mol-1, on the basis of the new value for DELTA(cr)g H(m)THETA C2(C6H5)2].