1. Basic ExperimentsAs a model experiment to analyse the malignant behavior of tumor cells, two kinds of transplantable rat ascites hepatoma cells (AH-62F and AH-66F) were investigated by a follow-up study on the metastic processes, and its results were compared with surface property of tumor cells which was examine by the colloid and Methylene Blue absorption method, and by cell electrophoresis.Marked differences were observed in biological properties between these two hepatoma cell lines; AH-66F showed a prodominent malignant behavior like short survival of the host rats and higher frequency of tumor formation in various organs and lymph nodes after interavenous ingculation However, frequency in liberation of tumor cells into the thoracic ducts did not vary greatly in both cases, in which tumor cells either of the two lines were inoculated into the colonic mesenterium.A marked difference was also found in electrokinetic properties between the two lines of these ascites hepatomas. The cell surface of AH-66F was constructed of substances containing electrically charged substances of higher density and particulary of sialic acid-dependent electrical charge, which was confirmed by measuring the decreased rate of electrical charge density of cell surface after treatment with sialidase.Based on these results, the electrokinetic properties of tumor cells was discussed and compared with their malignant behaviors.2. Electrokinetic property of human gastric cancer cells and their histopathological characteristics.The electrokinetic properties of human gastric cancer cells and all the surrouding mucosal cells were investigated comparatively by using cell electrophoresis. Cells were obtained from surgical specimens by treatment with collagenase and hyaluronidase immediately after their surgical removal.In all 20 cases, gastic cancer cells showed higher electrophoretic mobility than the mucosal cells. In the differentiated cases of gastric cancer, individual tumor cells were all uniform, while wide individual difference in electrophoretic mobilities was noted in the anaplastic cases of gastric cancer. In particul the latter cases showed higher avarage value in electrophoretic mobility than the formor.