A human neuroblastoma xenograft, designated TNB9, was used in this experiment. This xenograft is known to have a homogeneously staining region (HSR) on chromosome 20 and to exhibit 60- to 100-fold amplification of clones 8, G21 and N-myc, and showed a rapid tumor weight doubling time of 5.9 days; it represents one of the most malignant strains of human neuroblastoma. The effects of nine different chemotherapeutic agents on this xenograft were studied according to the standard Battelle Columbus Laboratories protocol, and the in vivo chemotherapeutic sensitivity assessment disclosed that Mitomycin C, Ifosfamide, and Carboplatin were highly effective against it, while VP-16, NK-171, 5-Fluorouracil, and THP-Adriamycin were ineffective. Cytogenetic and molecular-cytogenetic analyses suggest that the present data may accurately predict the clinical results with these chemotherapeutic agents in treating patients in advanced stages, as did those from our previous studies. Inclusion of Mitomycin C, Ifosfamide, and/or Carboplatin into a new chemotherapeutic protocol may be recommended.