Feasibility of utilizing human gastric cancers as first transplant generation xenografts in nude mice for determining tumor sensitivity to chemotherapeutic agents was demonstrated by applying subrenal capsule (SRC) assay. A total of 55 human gastric tumors from patients were tested in this assay. Mitomycin-C (MMC) and hexycarbamyl-5-FU (HCFU, 5-FU derivative) were selected for the treatment of these patients after surgery and also for this assay as first transplant. Evaluable rate of MMC in this assay was 92.7% and that of HCFU was 90.9%. Sensitivity of tumors to MMC was 25% and to HCFU was 32%. Correlation between response to chemotherapy of human tumors in patients and in nude mice was 78.6%. These results indicate that this assay could predict effective drugs for patients with gastric cancer.