Ehrlich Ascites Tumor Cells (JTC-11) reported here have been cultured in vitro for more than 3 years by pipetting, using 80% YLE+20% Bovine serum (final concentration: yeast exract 0.08%, lactalbumin hydrolysate 0.4%) as the medium. As the results of tissue culture experiments concerning the characteristics of this strain, I obtained the following conclusion. 1) This (JTC-11) K-Strain is the easiest group of acutual animal malignant tissue culture strains in points of cell preservation, culture-method (pipetting), stability, medium-unchanging during one subculture term, inoculum size and adhesion on the glass surface. 2) The proliferation rate is the greatest (about 2000 times for 8 days) and even a small number of cells have the ability of proliferation. 3) After the intraperitoneal reinoculation into female mice with more than 1.6×10(4) this strain cells, all the mice died by the tumor. Accordingly tumor producing capacity has been strongly preserved after a lapse of 3 years. 4) The strain-character (Sato) of this K-strain cells has still remained after in vivo 100 days transplantion through Cb-mice (Experiments of retissue-culture). 5) This K-strain cells have a interesting form, namely the small sucker-form podia appear at the tip of the processes.