Monolithic catalysts were prepd. on Al2O3-washcoated metal supports by using LaMnO3 perovskite or Pt-doped LaMn1-xPtO3 (x = 0.05-0.15) perovskites as active components. The partial substitution of Mn with Pt in the perovskite structure resulted in an increase in the perovskite catalytic activity in CO oxidn. The optimum compn. was LaMn0.9Pt0.1O3. The temp. and time of calcination did not show any significant effect on the activity of the Pt-doped perovskite. Its catalytic properties were not changed after 24 h long use at 900 degrees C.