Some new 4-hydroxy-l, 8-naphthyridin-2-one derivatives have been synthesized and reacted with some reagents giving: pyrono, acetoxy, arylmethylidynes, nitro, sulphonic, sul- phonylchloride, sulphonamide, sulphide, sulphine, oxathiine glyoxalyl chioride, formylchloride, arnides, azodyes, acetamide, isonitroso, cyanomethyl and metliyi derivatives. The structures of ali the new compounds have been established on the basis of elemental analysis and spec- troscopic data.