Three new compounds 2-4 and two known compounds 1 and 5 have been isolated from the cytotoxic fraction of an extract from a New Zealand mistletoe, Ileostylus micranthus. Compounds 1-5 are shown to be norditerpene lactones and have strong cytotoxicity. The compounds are proposed to have been assimilated by the mistletoe from the host tree, Podocarpus totara.