ABSTRACT To search for practical sources of potential useful taxoids and study the structure and activity relationship of taxoids, the leaves of Formosan Taxus mairei was extracted with n-hexane, ethanol, acetone and methanol, respectively. Extensive column and preparative thin layer chromatography by bioassay-directed screening resulted in the isolation of 8 taxoids. Their structures were identified as 2-deacetoxy taxinine J ¡]77¡^ ¡B1£]-hydroxy-5£\-deacetyl baccatin I¡]78¡^¡Btaxumairol Z¡]79¡^¡Btaxayuntin G¡]80¡^¡Btaxuspine F¡]81¡^¡B wallifoliol¡]82¡^¡Btaxumairol Q ¡]83¡^¡B1-deacetyl baccatin III¡]84¡^. The compound 82-containg fraction from another batch of material was acylated to yield a series of derivatives and their structures were identified as 7, 13-diacetylwallifoliol¡]85¡^¡B9, 13 - diacetyltaxumairol W¡]86¡^¡B7, 13-dibenzoylwallifoliol¡]87¡^¡B10, 13 - dibenzoyltaxacustin¡]88¡^¡B7, 9-dibenzoyl taxumairol P¡]89¡^ primarily on the basis of 1- and 2-D NMR techniques including DEPT, COSY and HMBC experiments as well as chemical correlation with know compounds. Among them, compound 79 ¡B83 was first isolated in nature, compounds 78 and 80-82 were first isolated from T. mairei and compounds 85-89 were new derivatives. All of these compounds were sent to National Research Institute of Chinese Medicine for antitumor test in vitro. The investigation of their structure and activity relationship is now in progress.