A new tannin, polygagallin, related to acertannin, is isolated from air-dried leaves of Acer ginnala Max. as prismatic crystals with 1/2 H$_{2}$O per mole, m.p.154-155.deg. and [.alpha.]$_{D}$$^{29}$ +43.79.deg. C. Polygagllin gives hexaacetate, m.p.164.5.deg. C, [.alpha.]$_{D}$$^{28}$ +42.deg. C, on treating with anhydroacetic acid and on treating with diazomethane, gives trimethyl ether, m.p.176.deg. C, [.alpha.]$_{D}$$^{22}$ +53.43, which yields triacetate, m.p.160.5.deg. C, [.alpha.]$_{D}$$^{22}$ + 132.5.deg. C, on acetylation and is not attacked by periodate. On hydrolysis, trimethoxypolygagallin yields one mole of polygalitol and that of trimethoxygallic acid. By the above results polygalallin has been established as 3-galloylpolygalito.ygalito.galallin has been established as 3-galloylpolygalito.