The thermal decomposition of copper(II) mellitate proceeds to completion between 470 and 530 K C6(CO2)6Cu3 --> 5.5CO2 + 0.03CO + [C3C6.5O1.0] by two distinct rate processes. The first is acceleratory and fits the power law (alpha1/2 = kt) to fractional reaction (alpha) = 0.45, during which the copper is extensively reduced (Cu2+ --> Cu+); the activation energy is 155 +/- 7 kJ mol-1. The second reaction is strongly deceleratory, being expressed by the third order equation; the activation energy is 200 +/- 15 kJ mol-1. Textural changes during reactions have been characterized by scanning electron microscope examinations. The salt does not show evidence of melting. The present work extends a previous investigation of the same reactant. Results here are discussed in the context of similar studies of copper(II) salts of other organic acids; all give evidence of stepwise cation reduction (Cu2+ --> Cu+ --> Cu) during the two consecutive reactions. It is concluded that, unlike other reactants in this comparison, the second step is not decomposition of copper(I) mellitate but involves a range of condensed aromatic anions. A short comparative survey is given of studies of the thermal decompositions of copper(II) salts of formic, oxalic, malonic, maleic, fumaric, squaric and mellitic acids.