A new antileukemic quassinoid glycoside, yadanzioside P, was isolated from "Ya-dan-zi", the seeds of Brucea javanica (L.) Merr. The structure was determined to be 3-O-(β-D-glucopyranosyl)-bruceantin by ¹H- and ¹³C-NMR spectral measurement and enzymatic hydrolysis. The NMR spectral inspection indicates that a quassinoid glycoside formulated as 3-O-(β-D-glucopyranosyl)bruceantin is not bruceantinoside B, but yadanzioside P.