The degree of imbalance in β°-Th and β+-Th as well as the frequency of the two forms in Sicilian β-thalassemic subjects have been studied. The hemoglobin synthesis in Rietti-Greppi-Micheli disease (RGMD) and in the β-thalassemia trait has also been studied. In an unselected thalassemic population, about 30% have been found to be β°-Th. Both groups of β°-Th and β+-Th showed severe imbalance with α/non-α ratio of 4.22 + 1.88 (SD) and 3.46 + 1.36, respectively. This difference was not statistically significant. In RGMD the α/non-α ratio was 2.12 + 0.36 while in the β-thalassemia trait it was 1.76 + 0.35.