Substituted LaMn1-yCoyO3 perovskite-type oxides (0.0 <= y <= 1.0), prepared by the citrate method, have been investigated as catalysts in the total combustion of acetylacetate. The characterization results indicate variation in specific surface area, crystal structure, infrared spectra and reducibility. The crystal phase transformation was found to occur for y(Co) values above 0.5. The role of Mn is to stabilize the cobaltite structure, which does not tolerate more than 30% substitution of Co for Mn. The catalytic activity in the total combustion of acetylacetate can be related with changes in the crystal structure and specific surface area. The higher intrinsic activity of the cobalfite doped with 10 wt% Mn, y(Co) = 0.9, can be explained by the changes in crystal and electronic properties. Magnetic properties (susceptibility, ZFC/FC and M-loops) show strong ferromagnetic interactions in the range (0.0 < y(Co) <= 0.5) while antiferromagnetism is progressively settled at higher cobalt concentrations. (C) 2008 Elsevier B.V. All rights reserved.