Polystyrene core-shell latex particles are introduced as affinity ligand carriers for affinity separations. The particles, prepared by a seeded emulsion polymerisation process, are submicron in size and composed of a hard polystyrene core surrounded by a hydrophilic shell to which affinity ligands can be covalently coupled. The reactive dye Cibacron Blue is studied as model ligand. This dye ligand, which is covalently coupled directly to hydroxyl groups on the particle surface, is studied and the amount of coupled dye is determined quantitatively by diffuse reflection spectroscopy. The degree of coupling can be controlled by the ionic strength of the reaction medium. The adsorption of bovine serum albumin to the latices appears to be proportional to the ligand density. The functionalised core-shell latices show a high colloidal stability, fast protein adsorption/desorption kinetics and a low non-specific adsorption. The latex particles can find use in affinity separation techniques such as affinity chromatography and affinity membrane filtration.