The profiles of the linear envelopes of surface electromyograms of seven major muscles in adults were studied as a function of walking speed. The ensemble statistical properties of average and standard deviation were used to quantitate the characteristics of the electromyographic patterns. Analysis of variance was used to indicate periods in the gait stride that were effected by walking speed. Two general types of pattern change were observed. One was that the fundamental phasing of muscle activity never changed but that relative amplitudes of the phases were modulated as speed increased. The other was that different phases of activity existed for different walking speeds. The timing of most phases (as expressed in percentage of the stride) decreased as speed increased. This suggests that the time base should be further normalized by stance and swing phases.