The authors describe a newly identified b 0 -thalassaemic mutation found in two subjects from two generations of a Slovak family. The b 0 -thalassaemic allele developed by insertion of one nucleoti- de (+G, CD 7/8) into the first exon of the beta-globin gene. The mutation causes a shift of the open globin reading frame which leads to the development of a terminal codon in codon 22. The thalassaemic allele is associated with the mediterranean haplotype IX. The mutation has in both heterozygotes the phenotype of b 0 -thalassaemia minor with a slightly elevated level of HbF.

        Key words: Thalassaemia- b-globin gene - Haplotype - Slovak population.