Spherical blastomeres of starfish embryos begin to adhere to neighboring blastomeres and to become columnar in shape from the 7(th) or 8(th) cleavage onward. Studying development of embryos in the presence of LiCl, we found that developmental changes in cell-cell contacts were accelerated by LiCl. In order to learn why LiCl increased the adhesiveness between blastomeres, the negative surface charge density was estimated by the method of cell electrophoresis. It turned out that the electrophoretic mobility (EPM) of all blastomeres isolated from LiCl-treated embryos before the 512-cell stage was remarkably decreased. At the mid-gastrula stage, however, when constituent cells were connected with each other more tightly, the EPM was significantly retarded irrespectively whether the cells had been isolated from control or from LiCl-treated embryos. From these results of cell electrophoresis we conclude that reduction of the negative surface charge density may be one of the important factors that enhance the adhesion of starfish embryonic cells.