The standard (p-degrees = 0.1 MPa) molar enthalpies of combustion in oxygen of each of the six dichlorophenols, at the temperature 298.15 K, were measured by rotating-bomb calorimetry from which the standard molar enthalpies of formation. in the crystalline phase were derived. The standard molar enthalpies of sublimation, at the temperature 298.15 K, were measured by microcalorimetry. -DELTA(f)H(m)degrees (cr)/(kJ.mol-1) DELTA(cr)H(m)degrees/(kJ.mol-1) 2,3-dichlorophenol (2,3-Cl2C6H3OH) 223.3+/-1.1 71.7+/-2.2 2,4-dichlorophenol (2,4-Cl2C6H3OH) 226.4+/-1.5 70.1+/-1.1 2,5-dichlorophenol (2,5-Cl2C6H3OH) 232.0+/-1.2 73.6+/-2.1 2,6-dichlorophenol (2,6-Cl2C6H3OH) 222.1+/-1.1 75.8+/-1.0 3,4-dichlorophenol (3,4-Cl2C6H3OH) 231.6+/-1.1 81.3+/-2.3 3.5-dichlorophenol (3,5-Cl2C6H3OH) 231.0+/-1.0 82.8+/-1.1 The derived standard molar enthalpies of formation of the gaseous compounds were compared with values estimated assuming the enthalpy increment for substitution of chlorine in phenol to be the same as for substitution into benzene.