alpha-Thalassaemias are probably the most common genetic disorder worldwide. alpha-Thalassaemias are haemolytic anaemias resulting from inherited deficient synthesis of alpha-globin chains. In this paper, the classification and nomenclature of alpha-thalassaemias are developed. Procedures to ensure the laboratory diagnosis are explained. The heterozygous carrier states for these disorders are, in most cases, not associated with any easily discernible change in the haemoglobin pattern, except, sometimes, a reduced MCV in the blood picture. Heterozygotes for alpha-thalassaemia deletions are now detectable by the accurate PCR method. Because of the high prevalence of these disorders in large segments of the world population, alpha-thalassemia and haemoglobinopathies often occur in the same individual. The laboratory features of these interactions and, particularly, the role of alpha-thalassaemia as a potential modulator of sickling haemoglobinopathies are discussed.