1. In 14 members of 26 cases of a family originating from Surinam a double heterozygosity (for thalassemia and for the abnormal minor component Hb-B2) was demonstrated. Thalassemia heterozygous carriers or individuals heterozygous for the Hb-B2 abnormality alone were not encountered.
2. The diagnosis of thalassemia minor was based on hematologic data. The abnormal minor Hb-component present in these cases was identified using the conventional electrophoretic and chromatographic technics and the fingerprinting method as being Hb-B2 (an abnormal Hb-A2). The percentages of the two minor Hb-fractions (Hb-A2 and Hb-B2) in these thalassemia heterozygous carriers are doubled, their sum being similar to the high level of Hb-A2 typical for most cases of thalassemia trait.
3. The genetic relationship between thalassemia minor (genotype: tT) and Hb-B2 heterozygosity (genotype: A2/B2) is discussed. The data on this pedigree are suggestive of a close linkage of the t-T and A2/B2-loci.