Abstract: Two new compounds were isolated from the chloroform soluble fraction of ethanolic extract of bark of Goniothalamus howii Merr. On the basis of their chemical properties and spectral data (MS, UV, IR,¹H and¹³CNMR) they were identified as 6S(1R-hydroxy-2R-cinnamyloxyphenethyl)5,6-dihydro- 5S-hydroxy-2-pyrone named Howiinol A and 6S-(1S,2R-epoxyphenethyl-5S-cinnamyloxy)5,6-dihydro-2-pyrone named Howiinin A. Howiinol A showed significant antitumor activities toward human tumor cell in vitro and in vivo and less toxic.