The resting potential of the cells the liver, renal cortex, spleen and cardiac muscle fiber of normal mice were measured by the glass micro-electode method, which resulted in the following values respectively: --40.6mV, --55.9mV, --62.8mV and --71.5mV. These potentials were also pursued as time lapsed until cardiac muscle fiber, a gradient decline first steeply until 30 minutes after and then further went down rather gradually when they were expressed as the absoluter, the gradients appeared less steeply and the final levels were as high as approximately --30mV. In the measurement conduced for the resting potential of implanted Ehrlich cancer cells at the time of seven to ten days after the implantation, the average potential for the first 10 minutes was --70.4mV and increased to --32.8mV at 120 minutes period.