The prevalence of eight mutations in 84 patients with beta-thalassaemia major and in 16 subjects with thalassaemia intermedia was investigated. All of the patients were Italian, originating from Eastern Sicily (Messina area) and some Calabrian regions. Genomic DNA was amplified by polymerase chain reaction (PCR). DNA molecular investigations were performed by allele-specific oligonucleotide (ASO) hybridization, to identify the following beta-thalassaemia mutations: CD39 (C-T), IVS1-110 (G-A), IVS1-6 (T-C), IVS1-1 (G-A), IVS2-745 (C-G), IVS2-1 (G-A), -87 (C-G), CD6 A (-A). Our data underline that in thalassemia intermedia two mutations were statistically prevalent: IVS1-6 T-->C (P < 0.001) and CD 6-A (P < 0.05). CD 39 was statistically prevalent in beta-thalassaemia major patients (P < 0.01). The difference between the two groups was not statistically significant for all the other mutations. Five different genotypes were recorded among thalassaemia intermedia and 15 among beta-thalassaemia major patients. Twenty-five percent of the intermedia patients and 4.5% of the major patients had homozygosity for mild mutations (group I); 62.5% of the intermedia patients and 26.2% of the major patients had combinations of mild/severe mutations (group II). In addition, homozygosity or double heterozygosity for severe mutations (group III) was found in 12.5% of the intermedia patients and 69% of the major patients. Some genotypes were restricted to thalassaemia intermedia, including heterozygosity -87/IVS1-6 and IVS1-6/CD 6-A. It is essential to understand the distribution and frequency of the relevant mutations in each population where beta-thalassaemias exist. This is of particular importance for genotype-phenotype correlation and for carrier detection, genetic counselling and prenatal diagnosis.