About one per cent of the Thai population are affected with thalassemic diseases. In each year there are almost 50,000 pregnancies at risk of having an affected fetus, one fourth of which result in thalassemic newborns. Both alpha- and beta -thalassemia, including hemoglobins E and Constant Spring, are common in Thailand. Their distribution varies from region to region and among different ethnic groups. About 30-40% of the population are carriers of at least one of the abnormal genes. Thalassemias and hemoglobinopathies are common and heterogeneous in Thailand. They combine to give more than 60 thalassemic syndromes with varying clinical severity. Abnormalities can be detected in every organ system. Studies in detail into each clinical problem will lead to better management. Hematological and molecular studies on different types of thalassemia in Thailand have made it possible to give prenatal diagnosis service to those pregnancies at risk of having a thalassemic child. Sporadic services have been given in three centers. Systematic prevention and control program is being planned by the cooperation of both the public and private sectors.