The methanol extract of the seed of Myristica fragrans (myristicaceae) demonstrated a potent inhibition on the proliferation of cultured human tumor cells such as A549 (non small cell lung), SK-OV-3 (ovary), SK-MEL-2(melanoma), XF498 (central nerve system) and HCT-15(colon). The MeOH extract was fractionated into three portions by serial solvent partition i,e., EtOAc soluble part, BuOH soluble part and remaining water layer. Among them, the EtOAc soluble part of the extract demonstrated a potent inhibition on the proliferation of cultured human tumor cells, Bioassay-guided fractionation of the EtOAc soluble part led to the isolation of six lignan constituents, i.e., safrole(1), machilin A (2), licarin B (3), macelignan (4), mesodihydroguaiaretic acid (5) and myristargenol A (6) as well as a large amount of myristic acid as active ingredients. Structures of the isolated active components (1-6) were established by chemical and spectroscopic means.