We performed in vivo chemosensitivity tests on human gastric carcinoma. To evaluate the efficacy of some combined chemotherapy for human gastric carcinoma maintained in the subcutaneous space in nude mice, we designed the following six experimental groups: 1) 5-FU group, 2) CDDP group, 3) CPT-11 group, 4) combined therapy group of 5-FU and CDDP, 5) combined therapy group of 5-FU and CPT-11, and 6) combined therapy group of CPT-11 and CDDP. An in vivo nude mice assay was performed. Histopathological changes of the tumors in nude mice, treated with anti-cancer agents,were also evaluated and compared to the results of the nude mice assay. Based on histopathological grading,the true positive rate of the nude mice assay was 0%, the true negative rate was 83.3%, and the accuracy rate was 83.3%. CPT-11 appeared to be highly efficacious when given in combination with CDDP in human gastric cancer cell lines. These results suggest that combination chemotherapy with CPT-11 and CDDP is clinically effective for gastric cancer patients.