Objectives of this paper were to elucidate essential electrical discharge patterns of lower limb muscles and their variabilities during a normal gait cycle.Subjects employed in the experiments were 217 healthy adults of both sexes, ranging in age from 18 to 22 years, and they had no disorder in the lower limb or the central nervous system in their medical history. Electromyograms (EMGs) were recorded from the Tibialis anterior (Ta), the Gastrocnemius lateral head (Gl), the Vastus medialis (Vm), the Gluteus maximus (Gm), the Rectus femoris (Rf), the Medial Hastrings (MH), and the Biceps femoris (Bf) by conventional method using surface electrodes. Angular changes of the ankle, knee and hip joints and time signals at the heel and the toe contacts with the ground were simultaneously recorded with the EMGs.The essential EMG pattern s of the lower limb muscles during a normal gait cycle were conclusively summarized: 1) The ankle joint muscles; i) The marked discharge of the Ta was observed in the period from the end of the swing phase to the early part of the stance phase, and in the period from the end of the stance phase to the early part of the swing phase. ii) The Gl showed the main discharge in the latter half of the stance phase, and showed almost complete electrical silence in the former half of the swing phase.2) The knee and hip joint muscles; i) The discharge of the Vm started at the latter half of the swing phase and increased abruptly just before or after the heel contact. The marked discharge of the Vm lasted into the first double leg support period. ii) The discharge of the Gm started at the latter half of the swing phase and increased just before or after the heel contact. The Gm showed the continuous discharge during the former half of the stance phase. iii) The main discharge of th Rf was similar to that of the Vm, and the Rf did not show distinguished activity in the former half of the swing phase. iv) The MH and the Bf showed the marked discharges from the the latter half of the swing phase to just before or after the heel contact, but little or no discharge in the former half of the swing phase.In addition to the essential EMG pattern s, the variations in the EMG patterns which were found to be within ranges of the normal activities were as follows: 1) The ankle joint muscles ; i) The distinguished discharge of the Ta at about the mid-swing phase appeared in about 85% of the subjects. ii) The discharge variation of the G1 was hardly observed during the gait cycle.2) The knee and hip joint muscles; i) The discharge of the Vm was seen around the mid-stance phase and in the second double leg support period in about 20% of the subjects. ii)The discharge variations of the Gm were similar to those of the Vm. iii) The discharge of the Rf appeared around the mid-stance phase in less than 20% of the subjects and at the end of the stance phase in about 80%. iv) In about 60% of the subjects the marked discharges of the MH and the Bf in the latter half of the swing phase decreased or disappeared abruptly around the heel contact; however, in the other 40%, the discharges continued until the midstance phase. The discharges of the MH and the Bf at the end of the stance phase were observed in less than 20% of the subjects.The marked discharges of the MH and the Bf decreased or disappeared abruptly at the moment when the Rf abruptly increased its electrical activity around the heel contact, and the spike sessation lasted until the moment when the Rf decreased its activity. It was suggested that the spike inhibition in the MH and the Bf might be due to an antagonistic inhibition caused by facilitation of the Rf.