Thermal behaviour of a series of ternary Co(II), Ni(II) and Cu(II) complexes with terephthalate ion and some aromatic diamines has been studied by thermogravimetric and differential scanning calorimetric techniques. Dehydration processes of the complexes are very similar-most of them lose water in a single step. Thermal stability of the dehydrated products increases in the order Co < Cu < Ni for 2,2'-dipyfidylamine and 2,2-bipyridine containing complexes, but Cu < Co < Ni for 1,10-phenanthroline containing complexes. The investigated compounds with 2,2'-bipyridine are always the most easily decomposed. The molar dehydration enthalpies are calculated and the possible decomposition mechanisms are assumed. Relations between thermal behaviour of the complexes and their crystal structures, type of central atom and aromatic diamine, as well as the presence of coordinated and/or lattice water molecules are discussed. (C) 2003 Elsevier B.V. All rights reserved.