The hydrated chlorides of noble metals located in the 8-10 groups of Periodic System were used in this work: Ru, Rh, Pd, Ir and Pt. The common mechanism of chloride compounds decomposition in oxidative, inert and reductive atmospheres was postulated and mutual similarities and differences were discussed. These compounds play a significant role in heterogeneous catalysis, as starting materials for metal/oxide catalysts, and also in analytical chemistry and industry. (C) 2005 Elsevier B.V. All rights reserved.