The aim of the present investigation was to verify a common view that thalassemia in Poland is a very rare disease. METHODS 600 patients (270 male and 330 female) aged 2-85 years with microcytosis and no evidence of iron deficiency were examined for beta-thalassemia. Hemoglobin A2 and hemoglobin F and bilirubin were evaluated. Patients with elevated A2 hemoglobin concentration were examined for 8 common Mediterranean mutations. RESULTS Hemoglobin A2 was increased in 106 patients. In 48 patients there was also an elevation of hemoglobin F and in 42 - of serum bilirubin. 7 different mutations were detected in 46 heterozygous patients (numbers of patients with a particular mutation are in square brackPis): IVS1-6(T>C) [15], IVS2-745(C>G) [14], IVS2-1(G>A) [10], IVS1-1(G>A) [2], CD6-A [2], CD39(C>T) [2], IVS1-110(G>A) [1]. CONCLUSIONS Frequencies of individual mutations in Poland were different from those encountered in Mediterranean and some Central European countries. Our data indicate that fl-thalassemia in Poland is not a rare disease and should be considered in differential diagnosis of hypochromic anemia.