In an attempt to estimate the prevalence ofβ0andβ+thalassemia genes in Greece chromatographic analysis of hemoglobins was performed in 30 children with homozygousβ-thalassemia prior to any transfusion. In 13 (43%) no HbA was detected, suggesting the presence ofβ0gene in the homozygous state (β0/βthal). In the remaining 17, HbA showed a bimodal distribution with values ranging from 4–36%. The detection of HbA suggests the presence ofβ+gene, while the bimodal distribution could be explained by the assumption that theβ+gene in single dose and in combination withβ0gene (β0/β+thai) results in the production of small amounts of HbA ranging from 4–11%, (first curve), while in double dose (β+/β+thal), in the production of higher amounts of HbA ranging from 24–36% (second curve). Theβ0/β+thai was observed in 11 (37%), and theβ+/β+thai in 6(20%). It is concluded that bothβ0andβ+genes are common in Greece and chromatographic analysis helps to determine the genotype of patients with homozygousβ-thalassemia.