The standard molar enthalpy of combustion of 2-chlorodibenzo-p-dioxin was redetermined using the sample of high purity by rotating-bomb calorimetry: Delta(c)H(m)(0)(cr) = -(5558.2 +/- 3.5) kJ (.) mol(-1). The values of standard molar enthalpies of formation were derived for crystalline and gaseous states: Delta(f)H(m)(0)(cr) = -(187.9 +/- 3.8) kJ (.) mol(-1) and DeltafH(m)(0)(g) = -(90.7 +/- 3.8) kJ (.) mol(-1). (C) 2003 Elsevier Ltd. All rights reserved.