The present review provides a summary of quantitative hemoglobin data and lists the results of gene mapping and sequencing analyses for blood samples from newborn babies of different countries. Methodology suitable for such studies is reviewed, various abnormal fetal hemoglobins are discussed, the occurrence of Hb Bart's (γ4) and of the embryonic chain is evaluated, and the various types ofγ-globin gene rearrangements (−Aγ. Aγ-;−Gγ. Gγ-;γ-thalassemia;γ-globin gene triplications, quadruplications, and quintuplications) are compared. The several tables list the frequencies of the common AγT variant and of the differentγgene rearrangements in various populations, while the results of quantitative analyses suggest that most anomalies are not associated with disease.