Hb Melusine [alpha 114(GH2)Pro-->Ser] was found in an Algerian patient during a systematic screening for hemoglobinopathies performed in Luxembourg. The abnormal hemoglobin was suspected when a thickening of the Hb A band was observed by isoelectrofocusing. The mutant hemoglobin was silent in all other electrophoretic methods used for presumptive diagnosis with the exception of globin electrophoresis in the presence of Triton X-100. This technique revealed an alpha chain considerably more hydrophobic than normal. The structural abnormality of Hb Melusine concerns position alpha 114(GH2) that belongs to a cluster of hydrophobic residues localized in the N-terminal half of the alpha T-12b tryptic peptide. It has been shown in the case of another variant of that position (Hb Nouakchott), that the replacement of the Pro GH2 by a Leu was responsible for a dramatic increase in the retention time of the alpha polypeptide chain during reversed phase high performance liquid chromatography, much higher than that reported for similar substitutions in other regions of the hemoglobin molecule.