Ceria-zirconia, solid solutions were prepared as thin, dense films on a 130-m(2)/g gamma-Al2O3 by Atomic Layer Deposition (ALD) for use as catalyst supports. Ce0.5Zr0.5O2 solid solutions were grown by alternating between Ce(TMHD)(4) and Zr(TMHD)(4) precursors during ALD cycles. 50 precursor-oxidation cycles resulted in a material with 0.77 g Ce0.5Zr0.5O2 per g gamma-Al2O3, corresponding to an average film thickness of 1.0 nm. The lattice parameter obtained from XRD was consistent with formation of a solid solution and scanning transmission electron microscopy (STEM) showed the mixed oxide was uniformly deposited. When impregnated with 1-wt% Pd, the ALD-prepared Ce0.5Zr0.5O2-gamma-Al2O3 catalyst showed CO-oxidation activity similar to Pd on bulk Ce0.5Zr0.5O2; however, the ALD-prepared sample maintained much of its surface area and catalytic activity when heated to temperatures up to 1273 K.