An accurate method for the quantification of carboxymethyllysine (CML) in food samples is evaluated. CML, a stable advanced Maillard compound, is considered as an useful marker of protein damage in severely heated foods. The proposed GC-MS method stipulates double derivatisation of amino acids and quantification by selected ion monitoring. Relative error of repeatability was further improved from 5 to 1% by replacing internal standard by isotope dilution. Comparison with enzyme linked immunosorbent assay (ELISA) was performed on infant formulas, with satisfactory results in powdered but not in liquid formulas. Quantification of CML in several food matrices allowed evidencing CML formation in food products containing reducing sugar only.