The aetiology and cellular mechanism of chronic inflammatory processes are poorly understood. Macrophages act prominently in the inflammatory response and we report here that they express two calcium-binding proteins. The expression of these proteins, referred to as MRP-8 and MRP-14, is specific for cells of myeloid origin, namely granulocytes, monocytes and macrophages, and is observed in blood granulocytes and monocytes but not in normal tissue macrophages. In acutely inflamed tissues, macrophages can express MRP-14 but not MRP-8, and in chronic inflammations, such as primary chronic polyarthritis, infiltrate macrophages express both MRP-8 and MRP-14. Characterization of MRP-8 and MRP-14 could therefore be useful to the understanding of cellular processes induced in chronic inflammation.