The coupling of fast protein liquid chromatography (FPLC) with inductively couples plasma mass spectrometry (ICP-MS) was evaluated as a technique for studying aluminium bound to proteins present in human serum. Separation of human serum proteins was achieved on a MonQ (HR5/5) anion-exchange column using an ammonium acetate gradient (0-0.25 mol I-1) at the physiological pH of 7.4 (0.05 mol l-1 TRIS-HC1 buffer). Aluminium contamination was avoided with an on-line Al-chelating scavenger column. Proteins were detected spectrophotometrically at 295 nm and the Al detection was carried out on-line using both quadrupole ICP-MS and double-focusing ICP-MS systems. At metal basal levels in serum the latter detector proved to be adequate for this detection. Results obtained with the procedure developed confirmed clearly that transferrin is the only significant A1-binding proteins in unspiked uraemic serum. In addition, a high-resolution ICP-MS instrument was applied successfully as an A1-specific detector allowing for the first time A1 speciation studies in unspiked normal serum. The technique can also be used for studying the protein binding of elements other than A1.