To determine the prevalence and geographic distribution of thalassemia and to evaluate the success of the thalassemia prevention and treatment programs in Iran. Data were obtained from the National Thalassemia Registry of Iran, Iranian Blood Transfusion Organization, genetic laboratories involved in prenatal diagnosis, related pharmaceutical companies, and centers performing bone marrow transplantation for thalassemic patients. A total of 13,879 living patients have been registered, mostly from the northern and southern parts of Iran with the median age of 15 years. Twenty-three percent of patients were older than 20 years. The number of newly diagnosed cases has been decreased considerably after the start of the prevention program. Since the introduction of prenatal diagnosis, 2819 couples (2549 fetuses) have been tested, with only 6 false results. Elective abortion was not performed in 10 affected fetuses. Most common mutations detected were IVS II-1 and IVS I-5. In 2003, approximately 25% of the national blood products and 6 million vials of desferal were used for thalassemic patients. Overall, 340 patients have received allogeneic bone marrow transplantation, of those 46 patients deceased. Bloodborne infections have also been decreased significantly owing to the national screening of blood products for bloodborne viral infections. Owing to the national prevention program and provided special care, the age distribution of thalassemic patients in Iran is getting adapted to a full prevention and treatment program and life expectancy of these patients has been increased considerably. This shift in the age distribution of thalassemia, a traditionally considered pediatric disease, will face us with new challenges and the health care system should be prepared for this new face of thalassemia.