Hemoglobin Southampton (also known as hemoglobin Casper) is a rare hemoglobin structural variant resulting from a substitution of a leucine residue for proline at codon beta106 [beta106(G8)Leu→Pro, CTG→CCG]. It is very unstable and associated with severe hemolytic anemia. We detected this mutation in a 37-year-old Uruguayan woman with a history of severe chronic hemolytic anemia since her childhood. According to our knowledge this is the first time that this variant has been found in the Uruguayan population.