Cerium-praseodymium mixed oxides covering a wide range of cerium/praseodymium ratios were synthesized, loaded with 2 wt% palladium, and characterized by X-ray diffraction and temperature-programmed reduction. Both the degree and average temperature of reduction of the catalyzed mixed oxides were found to increase with increasing praseodymium concentration. Quantitative results indicate that these materials may be useful, in conjunction with hydrocarbon traps, for treating automotive cold-start emissions.