The authors previously reported the advantages of a collagen gel embedded culture system for chemosensitivity tests for cancer. In this report, the chemosensitivities of surgically resected specimens were evaluated by the collagen gel embedded culture system and compared with the DNA ploidy pattern, measured by flow cytometry. The chemosensitivity and DNA ploidy pattern were determined in 11 patients with lung cancer, 8 with gastric cancer and 46 with colorectal cancer. Anticancer agents were MMC and CDDP at Cmax for one hour of exposure, and 5-FU, VDS, VP-16 and ADM at one tenth the Cmax for 24 hours of exposure. Results were compared with those of DNA histogram. In eight lung cancers which were demonstrated to be sensitive by the collagen gel system, 5 showed DNA aneuploidy (DA) and 3 DNA diploidy (DD). Seven cases (87.5%) of gastric cancer were demonstrated to be sensitive with the collagen gel system. Two of them showed DA and five DD. On the other hand, 19 cases (41.3%) of colorectal cancer were found to be sensitive, and 7 of them showed DA and twelve DD. Lung cancer and gastric cancer exhibiting aneuploidy demonstrated sensitivity with the collagen gel system, but the rate of sensitivity was only 28% in colorectal cancer, and even aneuploidy cases showed a low sensitivity.