In accordance with the present invention, there are provided derivatives of chemotherapeutic agents (e.g., paclitaxel), which serve as bifunctional agents. Invention derivatives retain the antitumor activity of the parent compound, and, coupled with the electron affinic substituents thereon, produce compounds which show a strong capability for radiosensitizing tumor cells growing in vitro. It is expected that a single drug which combines the properties of a radiosensitizer with chemotherapeutic activity will offer significant advantages not only to patients, but also to radiotherapists seeking improved modes of treatment. The combination of antitumor properties with electron-affinic function produces novel radiosensitizers, a second generation of drugs which are more powerful to fight cancers. Bifunctional agents with the dual properties of tubulin assembly and electron affinity will make the compounds useful not only as radiosensitizers, but also as cytotoxins.