Reproducible and accurate myocardial T* 2 measurements are required for the quantification of iron in heart tissue in transfused thalassemia. The aim of this study was to determine the best method to measure the myocardial T* 2 from multi-gradientecho data acquired both with and without black-blood preparation. Sixteen thalassemia patients from six centers were scanned twice locally, within 1 week, using an optimized brightblood T* 2 sequence and then subsequently scanned at the standardization center in London within 4 weeks, using a T* 2 sequence both with and without black-blood preparation. Different curve-fitting models (monoexponential, truncation, and offset) were applied to the data and the results were compared by means of reproducibility. T* 2 measurements obtained using the bright-and black-blood techniques. The black-blood data were well fitted by the monoexponential model, which suggests that a more accurate measure of T* 2 can be obtained by removing the main source of errors in the bright-blood data. For bright-blood data, the offset model appeared to underestimate T* 2 values substantially and was less reproducible. The truncation model gave rise to more reproducible T* 2 measurements, which were also closer to the values obtained from the blackblood data. Magn Reson Med 60:1082-1089, 2008.