The monolithic catalysts prepd. by calcining a La(NO3)(3) + Co(NO3)(2)mixt. (3 hrs./750 degrees C) to form the LaCoO3 perovskite active phase, BET sp. surface 6.6 m(2)/g, were most active in the oxidn. (96%) of 10,000 h(-1) (1:99 v/v) CO-air at 404 degrees C. Conversion of CO fell in the descending order of LaCoO3 precursors: nitrate > carbonate > hydroxide, and also as the amt. of the active phase was reduced (from 22.7 to 11.7% LaCoO3), and as the calcination temp. was increased (to 900 or 1200 degrees C). Poly(vinyl alcohol) used as solvent to coppt. La and Co carbonates and to increase the BET surface of perovskite was ineffective.