The catalytic behaviour of LaMnO3, LaCoO3 and (La0.84Sr0.16 )(Mn0.67Co0.33)O-3 perovskites supported on cordierite monoliths was studied in the total oxidation of chlorinated hydrocarbons (CHC). By-products (higher chlorinated hydrocarbons, lower molecular coupling and cracking products) were formed in the low temperature range depending on the kind and concentration of CHC in the feed and the reaction conditions. The preparation method (impregnation or coating) influences catalytic activity and by-product formation. Addition of water, methane or propane to the feed diminishes the by-product formation significantly. In the case of monolith supported LaCoO3 perovskite, an irreversible catalyst deactivation was observed. (C) 2000 Elsevier Science B.V. All rights reserved.