A methanol extract of the peels of Citrus sudachi gave five new compounds (1-5) and 27 known compounds. Thestructures were elucidated on the basis of spectroscopic evidence. Several of these compounds were assayed forantimicrobial activity against methicillin-resistant Staphylococcus aureus and Helicobacter pylori, and sudachitin (6)and 3'-demethoxysudachitin (7) were the most active.