Three novel bioactive acetogenins, gigantransenins A (1), B (2), and C (3), were isolated from the bark of Goniothalamus giganteus (Annonaceae). 1-3 are C-37 mono-tetrahydrofuran (THF) acetogenins each having a trans double bond; their absolute structures were elucidated by spectral and spectroscopic analyses and derivatizations. No Annonaceous acetogenins having trans double bonds have been reported previously. 1-3 showed selective inhibitory effects on the human breast tumor cell line (MCF-7) that are comparable with the potency of adriamycin. Copyright (C) 1996 Elsevier Science Ltd