This is a five-year renewal application for the Thalassemia Clinical Research Network (TCRN). TCRN's mission is to accelerate research in the management of thalassemia. Syndromes encompassed by this mission include the [unreadable] thalassemias: homozygous or compound heterozygous plus Hemoglobin E/[unreadable] thalassemia;and the alpha thalassemias: homozygous, hemoglobin H disease, and HbH/Constant Spring. The network is composed of four core U.S. sites, a data coordinating center, several large affiliated clinical sites in the U.S., Canada, and England, and several smaller regional "satellite" sites to the core centers, in a cooperative agreement with NHLBI. Key strengths of the TCRN include a demonstrated ability of the investigators and sites cooperatively to standardize patient assessment and care;to design, implement and conduct clinical trials with observational, interventional, and ancillary designs. The multicenter network has been crucial due to sample size considerations. A pivotal accomplishment of the initial grant period is the establishment and analysis of the TCRN Registry, from which subjects for trials are identified. The registry now includes over 800 patients from 22 sites, including [unreadable]-thalassemia major (n=422), [unreadable] -thal intermedia (n=121), Hb E/ [unreadable] thal (n=103), transfusion-dependent a-thal major (n=9), HbH disease (n=l 05), and HbH/Constant Spring (n=44). The Specific Aims of the renewal grant are: (I) To perform interventional clinical trials in key areas of thalassemia care. Two trials are proposed. First, a randomized, controlled trial to examine the effect of deferoxamine alone v. deferoxamine plus deferiprone, on cardiac disease due to transfusional iron overload. Second, a randomized trial of arginine v. placebo for pulmonary hypertension, an important problem in thalassemia intermedia and other hemolytic states. (II) To provide an infrastructure for development, launch, and prompt completion of small, innovative trials in thalassemia. (Ill) To improve assessment of phenotype and clinical outcomes in thalassemia, in order to facilitate current and future clinical trials. This will be accomplished by two studies. The Thalassemia Longitudinal Cohort study, as well as a detailed study of iron-related organ damage, comparing measures of iron burden in the heart, liver and pancreas, to outcomes of iron-related organ dysfunction. Combined with the proposed clinical trials and the ability to perform detailed genotype/phenotype correlations, these improved phenotype and outcome measures are powerful tools to enhance knowledge about thalassemia clinical care, as envisioned by the NIH's 2003 Director's Roadmap.