A 25-year-old male had a life long history of a hemolytic anemia which was shown to be due to the presence of an unstable hemoglobin, Hb Atlanta beta 75 Leu leads to Pro. Two dimensional peptide maps of isopropanol precipitated globin also showed the presence of a second variant, Hb Coventry beta 141 Leu deleted. HPLC separation of the tryptic peptides consistently demonstrated both the abnormal and normal beta 9 and beta 14 peptides in the digest of total globin. Neither of the abnormal peptides was apparent on similar maps of globin from his parents or his two siblings. The proportion of the variants measured from the peptide maps was 11% beta-Coventry, 34% beta-Atlanta and the remainder beta-A. The possible basis for the presence of three beta-globins is discussed and it is concluded that this is likely to be due to some mechanism other than a beta-delta cross-over.