Carbon monoxide adsorbs reversibly into organic suspensions of a series of colloidal poly(vinylpyrrolidone) stabilized bimetallic palladium-copper alloys with particle sizes of ca. 45 Angstrom, binding to both copper and palladium sites. The relative intensities of the [CuCO] and [PdCO] infrared absorptions of the as-prepared bimetallic colloids in the presence of saturated solutions of CO reveal the preference of palladium for surface sites on the alloy particles, in contrast to the more commonly observed surface segregation of copper in the bulk alloy. The IR spectrum of adsorbed CO at room temperature is time dependent over several days, in a manner suggesting a rearrangement of the surface atomic layers of the particles with further enrichment in palladium.