 Alpha thalassemia is a genetic disorder characterized by anemia and a clinical phenotype that varies from asymptomatic to lethal hemolytic anemia. It is the most common monogenic gene disorder in the world, especially in Mediterranean countries, Southeast Asia, Africa, the Middle East and the Indian subcontinent. The disease results from deletion of one or both alpha genes on chromosome 16, which leads to a decrease in the number of functional alpha-globin genes. The severity of the disease depends on the genotype-phenotype correlation, with HBH disease being the most severe form and hemoglobin-Barth's hydrops-fetalous syndrome being the lethal form. Molecular analysis is usually required to confirm the diagnosis. Genetic counseling is offered to couples at risk for HBH disease or hemoglobin-Barth's hydrops-fetalous syndrome and carriers of alpha-plus or alpha-zero thalassemia alleles generally do not need treatment. HBH patients may require intermittent transfusion therapy during illness and most pregnancies in which the fetus is known to have hemoglobin-Barth's hydrops-fetalous syndrome are terminated due to increased risk of maternal and fetal morbidity.