Included within the scope of the present invention are potent taxanes and taxanes containing a linking group. Also included is a cytotoxic agent comprising one or more taxanes linked to a cell binding agent. A therapeutic composition for inducing cell death in selected cell populations comprising: (A) a cytotoxic amount of one or more taxanes covalently bonded to a cell binding agent through a link, and (B) a pharmaceutically acceptable carrier, diluent or excipient is also included. A method for inducing cell death in selected cell populations comprising contacting target cells or tissue containing target cells with an effective amount of a cytotoxic agent comprising one or more taxanes linked to a cell binding agent is included as well.