In 29 Czech and Slovak families with the most frequent and newly identified beta-thalassaemic alleles and with some structural haemoglobin variants (Hb E, Hb Haná, Hb Santa Ana) haplotypes of the beta-globin locus of alleles with these mutations were identified. In most instances haplotypes I and V were involved which were found in 57% of the patients. The bond of the most common beta-thalassaemic mutation: IVS-I-1, IVS-I-110, CD 39 (C-T), IVS-II-745, IVS-I-6 with alleles with the same haplotypes as in the mediterranean region suggests a mediterranean origin of these mutations. In Hb Santa Ana a hitherto not described haplotype was identified (-(+)-(-)-(+3), indicating a de novo origin of the mutation. Also in newly identified beta-thalassaemic mutations in CD 7/8 (+G), in CD 38/39 (-C) and in HbE and Hb Haná de novo development is probable.