Walking on both outdoor and indoor surfaces requires the ability to negotiate connections between vertical distances, simply known as hills and stairs. Therefore, the purpose of the present study was to evaluate the muscle activity patterns of the TFL and ADL during both hill and stair walking. We hypothesized that TFL and ADL activity during initial swing, initial stance, and late stance of up-ramp and up-stair walking would be greater than level walking. In contrast, we hypothesized that both TFL and ADL activity during initial swing of down-ramp and down-stair walking would be less. We utilized a 15° ramp, a 35° stair set, and for comparison of this steep angle, we also collected data on a 33° ramp. During up-ramp and up-stair walking, TFL and ADL activity during both initial swing and late stance of the up conditions were greater than level walking. For the down conditions, ADL activity during the swing phase of the steep down-ramp was less. Practically, our muscle activity results demonstrate that the hip abductors and hip adductors may provide additional pelvic stability and supplementary thigh acceleration during ramp and stair walking.