The antitumor effect of vinblastine (VBL), vincristine (VCR), etoposide (VP-16), teniposide (VM-26), cisplatin (CDDP), CBDCA (JM-8, Carboplatin), CHIP (JM-9), DWA2114R and recombinant human tumor necrosis factor (TNF) on four human testicular cancers heterotransplanted in nude mice were studied. The treatments with CDDP, CBDCA or CHIP significantly reduced the transplanted tumors. Combination chemotherapy with CDDP, bleomycin and VBL or VCR or VP-16 or VM-26 also revealed significant tumor regression. The antitumor effect of TNF on human testicular xenografts was much more evident when it was given intratumorally than when given intravenously. Teratoma was resistant to TNF even when it was administered intratumorally. Those results are briefly discussed and compared with the clinical results of chemotherapy. Several problems in anticancer drug sensitivity test against human tumor xenografts are also discussed.