A water-soluble and stable camptothecin derivative, CPT-11, was found to possess a strong antitumor activity against various murine tumors. In the present study, CPT-11 was tested against ten human gastrointestinal cancer xenograft lines carried by nude mice. CPT-11 was very effective against nine xenograft lines, with the exception of one xenograft. On the other hand, VP-16 was ineffective against all these xenograft lines. Therefore, CPT-11 is expected to be clinically more effective against gastrointestinal cancer than the topo II targeting agent.