In this study we have carried out α-globin gene mapping, hemoglobin (Hb) Bart's quantitation serum bilirubin, and red blood cell indices determination in a group of Sardinian appropriate for gestational age premature infants (from 32 to 35 wk gestation) in order to define the incidence in this population of the different α-thalassemia syndromes, their expression rate, and the correlation between the α-globin genotype and phenotype at this developmental stage. The gene frequencies of deletion (-α) and nondeletion (ααth) α-thalassemia were 0.29 and 0.04, respectively, and thus not different from those found in full-term newborns from the same population. The majority of premature newborns with a single α-globin gene deletion [(-α/αα) genotype] were hematologically silent. Those who manifested increased Hb Bart's (1.2 to 3.4%) had slightly reduced Hb levels (17.4 ± 2.6 g/dl), mean corpuscular volume (102.6 ± 6.3 fl), and mean corpuscular Hb (34.8 ± 2.0 pg) values. Those infants with the deletion of two α-globin structural genes (-α/-α) showed without exception moderate amount of Hb Bart's in the 3.5-8.1% range and an obvious decrease of Hb levels (16.1 ± 1.6 g/dl) mean corpuscular Hb (30.6 ± 3.5 pg), and mean corpuscular volume (88.5 ± 11.5 fl) values. The only infant with the deletion of 3 α-globin structural genes had 25% Hb Bart's associated with a moderate microcytic anemia at birth and developed the clinical picture of Hb H disease. Carriers of nondeletion α-thalassemia (αα/ααth) showed variable amount of Hb Bart's always associated with thalassemia-like red cell indices. Higher Hb Bart's levels were observed in those subjects carrying the initiation codon mutation of the α2 gene as compared with carriers of other nondeletion α-thalassemia defects.