Six new annonaceous acetogenins, 12,15-cis-squamostatin-D (1), 12,15-cis-squamostatin-A (2), artemoin-A (3), artemoin-B (4), artemoin-C (5) and artemoin-D (6), along with eleven known ones, were isolated from the seeds of Formosan Annona atemoya. The structures of these isolates were established on the basis of mass and related spectral evidence. All of them, except for four linear annonaceous acetogenins, exhibited potent cytotoxicity against Hep G2, Hep 2,2,15, KB, CCM2 and CEM cancer cell lines.