The hereditary anaemias present a major genetic health problem that contributes considerably to childhood mortality and morbidity in many developing countries. This article summarizes recent scientific and technical advances in knowledge concerning the genes involved and their interaction to produce major haemoglobinopathies, the clinical pictures of these conditions, and their diagnostic criteria. Though there is no definitive cure, supportive treatment for the haemoglobinopathies has improved significantly, offering better quality of life and improved survival, and should be attempted for all such patients. For sickle cell disease, this comprises a simple set of rules that should be incorporated into existing medical care, whereas for thalassaemia, a regimen of intensive blood transfusion and regular subcutaneous infusion of deferoxamine is recommended. This treatment is stressful and probably too expensive to be applied in many developing countries until the birth rate of patients needing it can be sufficiently reduced by community control programmes.