We have evaluated the mutation profile in a sample of 127 unrelated β-thalassemia (β thal) individuals, diagnosed through A2 and fetal hemoglobin quantification by high-performance liquid chromatography (HPLC) from the Brazilian southernmost state, where a flow of Italian immigrants had occurred in the late 19th century, mainly from Northern Italy. The molecular analysis was performed by DNA sequencing of the most common mutations found in the Mediterranean region. The β0 codon 39 nonsense mutation was the most frequent alteration (50.9%), followed by β+ IVSI 110 G>A (18.1%), β0 IVSI 1 G>A (12.9%), β+ IVSI 6 T>C (9.5%), and other rare mutations (8.6%). The chosen gene sequence was able to identify 91% β-thal mutations in the population studied, showing some similarity with allele frequencies of the mainly colonizing countries of Rio Grande do Sul state. The comparison of our results to other Brazilian studies has shown significant differences. Therefore, we can conclude that the genotypic profile of β-thal shows great variability. Hence, it would be arbitrary to infer regional study results as being representative of the Brazilian whole population. Brazilian researchers of different regions should identify their most frequent genotypes to provide better understanding on this disease and state adequate public health policies. © Springer-Verlag 2007.875381384Araujo, A.S., Silva, W.A., Leao, S.A., Bandeira, F.C., Petrou, M., Modell, B., Zago, M.A., A different molecular patterns of beta-thalassemia mutation in northeast Brazil (2003) Hemoglobin, 27, pp. 211-217Bertuzzo, C.S., Sonati, M.F., Costa, F.F., Hematological phenotype and the type of β-thalassemia mutation in Brazil (1997) Braz. J. 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