Two new taxoids, taxezopidines M (1) and N (2), have been isolated from seeds of the Japanese yew, Taxus cuspidata, and new structures were elucidated on the basis of spectroscopic data. The absolute configuration of a 3-N,N-(dimethylamino)-3-phenylpropanoyl group in 1 and 2 was determined to be R in each case by chiral HPLC analysis. The effect of 1 and 2 on the CaCl(2)-induced depolymerization of microtubules was investigated.