The methanolic extract from the rhizome of Hedychium coronarium was found to inhibit the increase in vascular permeability induced by acetic acid in mice and nitric oxide production in lipopolysaccharide-activated mouse peritoneal macrophages. From the methanolic extract, three new labdane-type diterpenes, hedychilactones A, B, and C, were isolated together with six known diterpenes. The structures of hedychilactones were elucidated on the basis of chemical and physicochemical evidence. The diterpene constituents showed inhibitory effects on the increase in vascular permeability, nitric oxide production, and inducible nitric oxide synthase induction.