Flavanone glycosides in the peels of Citrus and Poncirus were examined by thin-layer chromatography. The results obtained from the analysis of eleven Citrus species and one Poncirus species show that each species has an ability of synthesizing both flavanone neohesperidosides and flavanone rutinosides. This fact is out of accordance with the proposals made by Horowitz and Nakabayashi. In all the species of subgenus Metacitrus examined, hesperidin is present as a main flavanone component. On the other hand, the results obtained from Archicitrus species are complicated.