Hemoglobin Arlington Park was detected accidentally as result of the use of a hemolysate which contained hemoglobin with normal electrophoretic mobility as a control for peptide mapping. Peptide maps of this hemolysate revealed 3 new peptides resulting from 2 amino acid substitutions to give to new variant with the composition (beta6 Glu replaced by Lys, 95 Lys replaced by Glu).