Two types of alpha+ thalassemia (-alpha l) have been described, respectively termed leftward and rightward, which correspond to nonhomologous crossing-over in different homology zones X and Z within the alpha-globin gene cluster. Up to now the leftward type has been described only in Asiatic populations, whereas the rightward type is universally distributed. We report here a first case of leftward deletion observed in a Sicilian male. This raises the question of an identical or not crossing-over event.