Gold complexes with sulfur donor ligands have long been used to treat arthritis. In most cases, polymeric gold(I) complexes are used. Frequently, the exact structure of the compounds is not known. It appears likely that the thiophilic metal ions attack sulfur containing amino acid residues of enzymes (e.g. of collagenase) and thus inhibit their function. Studies confirm an intracellular exchange with the small peptide glutathione. Typical examples are complexes with thiomalic acid, thioglucose or thiopropanolsulfonate.