Paclitaxel (Taxol), one of the most potent anticancer drugs, is a microtubule-stabilizing compound that inhibits microtubule depolymerization within the cell. The structure of paclitaxel is composed of two key elements, a taxane ring and an N-benzoylphenylisoserine side chain at C-13. A number of natural and artificial compounds with taxane skeletons have been isolated, but almost none of their bioactivities have been evaluated. In this study, we focused on compounds having a taxane skeleton structure and examined their effects on tubulin dynamics. Although none of these compounds had an N-benzoylphenylisoserine side chain, three were found to promote tubulin assembly. On the other hand, one compound inhibited tubluin assembly in a way similar to nocodazole. These compounds exhibited novel structure-activity relationships of taxane compounds.