SUMMARYBackground: Beta-thalassaemia is a congenital disorder caused by point mutations in a haemoglobin beta-globin chain. The heterozygous form produces microcytosis and normal iron levels, however, haemoglobin electrophoresis shows elevated amounts of haemoglobin A 2 and eventually foetal haemoglobin F as well.Methods: Between 2005-2011, in three centres in Slovakia, carriers of beta-thalassaemic genes or other haemoglobinopathies were searched for. Diagnosis was performed by haematologists whereby the family history was evaluated, together with the overall clinical condition, blood count and blood smear, iron parameters, haemolysis and haemoglobin electrophoresis testing. A proportion of patients was examined by molecular genetic methods.Results: A clinical suspicion of the heterozygous form of beta-thalassaemia was documented in 402 patients (21.9%) out of a total of 1,834 examinations. From these patients, 87 underwent molecular genetic testing and mutations of beta globin genes were identified in 70 of them, where the most frequent mutations were IVS 2.1 (28.5%), IVS 1.110 (25.6%) and IVS 1.1 (11.3%). Evidence of haemoglobin S (sickle cell anaemia) was also notable in one case (patient of African origin). Unusually high levels of haemoglobin F (6-21%) were found in 23 adult subjects.Conclusion: The study showed that there is a higher number of heterozygotes for beta-thalassaemia and rarely haemoglobinopathies. It is necessary to continue in search of pathological gene carriers in Slovakia.