Thalassemia and abnormal hemoglobins are common genetic disorders in Asia. Thalassemia is not only an important public health problem but also a socio-economic problem of many countries in the region. The approach to deal with the thalassemic problem is to prevent and control birth of new cases. This requires an accurate identification of the couple at high risk for thalassemia. However, the diagnosis of thalassemia carrier states need several tests which are not practical for screening the population at large. Recently we have used two simple laboratory tests to screen for potential thalassemia carriers and hemoglobin E individuals. There is also a new development in using the automatic HPLC to diagnose thalassemic diseases and the carriers. This system gives both qualitative and quantitative analysis of hemoglobin components in the same run with good precision and reproducibility. The system has been applied to study thalassemia and abnormal Hb in adult and cord blood. This system has enabled us to do both prenatal and postnatal diagnosis of thalassemia within the few minutes. However, none of these screening tests can accurately give specific diagnosis of the thalassemia genotype. Specific thalassemia mutation can be carried out by DNA analysis. Many DNA techniques have been used for point mutation detection and small deletion. For the last few years there is a development of DNA chip technology that has been applied for thalassemia mutation as well. Clinically, thalassemia is very heterogeneous in the manifestation. In spite of seemingly identical genotypes, severity of beta thalassemic patients can vary greatly. Heterogeneity in the clinical manifestation of beta thalassemic diseases may occur from the nature of beta globin gene mutation, alpha thalassemia gene interaction and difference in the amount of Hb F production which is partly associated with a specific beta globin haplotype. However, there is still some beta thalassemia cases that have a mild clinical symptom without those known genetic fators interaction suggesting that there are other additional factors responsible for the mildness of the disease.