Four molecular forms of transferrins with different iron-binding states were separated by HPLC using a pyridinium polymer column. The elution order was monoferric transferrin bound to the C-site, holotransferrin, apotransferrin and monoferric transferrin bound to the N-site. Human sera were also analyzed with the column, and ICP-MS combined with HPLC was used to detect iron in each peak. Transferrin peaks separated by HPLC were also confirmed by an immunological method. The percentages of iron saturation in transferrins obtained by the HPLC method were compared with the values calculated from clinical data.