This study concerned the evaluation of β-thalassemia alleles in nearly 50 patients with β-thalassemia major and in 130 -thalassemia heterozygotes using gene amplification and dot-blot hybridization with synthetic probes. Fourteen different mutations were observed (Table I); of these, three (IVS-I-110; IVS-I-6; IVS-I-1) account for some 75% of all β-thalassemia alleles. Newly discovered variants, i.e. T ↣ C in the initiation codon and AATAAA ↣ AATGAA in the poly A site were observed in a few patients. the poly A mutation with classicall β-thalassemia alleles result in thalassemia intermedia. Hb Lepore is a rather common abnormality and combinations of this variant with β-thalassemia often result in severe disease; a search for β-thalassemia mutations among patients affected with this disease should include an analysis to detect this hemoglobin abnormality.