An effect of an electric field on proliferation and on differentiation of cultured muscle cells has been studied in vitro. C2C12 (the mouse myoblast cell line originated with the cross-striated muscle of C3H mouse) was exposed to electric stimuli. In the first experiment, the adhered cells were exposed to the electric field between two electrodes made of platinum wire of 0.2 mm diameter dipped in the medium at 37 degrees Celsius for 72 hours. The electric pulses at a period of one second with a pulse width of 0.1 second were generated with a function generator. Variation was made on the pulse amplitude < 12 V. The number of adhered cells was counted after exposure to electric stimulation. In the second experiment, the cells were cultivated for 96 hours without electric stimulation in an incubator, after electric stimulation of 0.1 V for 72 hours. After incubation, the movement of myotubes was observed with electric stimulation at a period of one second with a pulse width of one millisecond of 30 V. The experimental results show that cells adhere and proliferate under electric pulses lower than 8 V, and that differentiation accelerates with the electric pulses of 0.1 V.