Variety of outward voltage-dependent currents in cultured frog myoblasts were registered by means of whole cell voltage clamp. Six types of potassium currents (Ik) which reach the peak value (-10 mV) in 5, 12, 20, 30, 50 ms (fast) and do not reach the maximum in 7 s (slow) were established. High sensitivity to low temperature (+5 degrees) was shown for channels of very fast and of slow non-inactivated Ik. The assumption is made that some of Ik--5, 20 and 30 ms to peak are especially characteristic of myoblasts fusion stage.