The perovskite-type oxides La 1−x Sr x MO 3 (M=Co 0.77 Bi 0.20 Pd 0.03 ) have been investigated for three-way catalytic performance and characterized by means of temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalysts exhibited good activity in CO elimination: La 0.8 Sr 0.2 MO 3 showed ca. 100% CO conversion at 160°C, 60000h −1 , and λ=1.00. Under similar reaction conditions, the activity for C 3 H 6 elimination decreased in the order of La 0.2 Sr 0.8 MO 3 >La 0.8 Sr 0.2 MO 3 >La 0.4 Sr 0.6 MO 3 >La 0.6 Sr 0.4 MO 3 >LaMO 3 , while the activity for NO elimination decreased in the order of La 0.8 Sr 0.2 MO 3 >La 0.2 Sr 0.8 MO 3 >La 0.4 Sr 0.6 MO 3 >La 0.6 Sr 0.4 MO 3 >LaMO 3 . With x<0.6, La 1−x Sr x MO 3 were single-phase and hexagonal in structure; at x=0.6 and 0.8, they were cubic and there was a trace amount of the La 2 O 3 phase. The results of TPD, TPR, and XPS studies revealed the coexistence of over-stoichiometric oxygen vacancies in La 0.8 Sr 0.2 MO 3 , a criterion for good three-way catalytic performance.