Children with beta thalassemia major, also called Cooley's anemia, usually develop clinical signs during their first year of life. They appear to be malnourished and may exhibit abdominal girth expansion. They show skeletal deformations, which are a result of increased erythropoiesis. A common finding is facial bone changes.

Other clinical signs include frequent infections, hepatomegaly, splenomegaly, cardiomegaly, gall stones, leg ulcers, and poor growth and sexual development.

Death usually occurs by the time these patients are in their early twenties unless treated with blood transfusions along with iron-chelating agents. If no chelating agent is used during treatment life will only be prolonged by about a decade.

Beta thalassemia is found most often in populations of people from the Mediterranean, southern China, and India.