P3 cell lines can be grown in protein- and lipid-free synthetic medium. Using the P3 cell culture, we have shown that these cells produce autocrine growth factors and cell-substrate attachment factors. Because the cultured cells produce proteinase-inhibitor, spent medium is applicable for inactivating the action of trypsin at the time of cell passage. In addition, we have tried to cultivate various types of cells in serum-free media on the market (ASF103, ASF104 and GIT). Many cell lines can grow in these media, but inoculum dependency is observed in some cell lines. Production of monoclonal antibody by a hybridoma cell line is rather enhanced in these media. These media can be preserved at 4 degrees C or -20 degrees C for a relatively long period. These media added with EGF support the growth of Syrian hamster embryo cells at an early passage. The growth of human diploid fibroblasts in GIT medium added with EGF is a little less compared in a serum-containing medium.