This study examined the locomotor behavior of the Galago garnetti, a prosimian. The recruitment patterns of the vastus lateralis (VL) and biceps femoris (BF) were investigated, and the excursion patterns of the hip, knee, and ankle joints were estimated, during quadrupedal horizontal walking, vertical climbing, and vertical descending on poles. In horizontal walking, the period of VL muscle activity almost coincided with that of increasing knee joint angle, although the VL ceased activity at about 80% of stance phase, while the knee joint angle continued to increase. One reason that this occurs is that the opposite hindlimb touches down at roughly 80% of stance phase, so the body weight can shift to the opposite hindlimb before toe-off. Another reason is that other knee extensor muscles may assist this motion. The BF showed sustained activity in both stance and swing phase in horizontal walking, with marked activity at mid-stance and mid-swing phase. The former peak coincided with the period during which the hip joint angle increased, and the latter peak occurred when the knee was being flexed. The trunk angle with respect to the substrate and the fact that the VL did not exhibit consistent activity during vertical descending, suggests that the garnet galago supports its body mainly with the forelimbs while descending. During vertical climbing, the lower part of the body was relatively close to the substrate. The galago protracted its hindlimb further backward to support the body in stance phase. Consequently, the hip and knee joints tended to be extended more during vertical climbing than during horizontal walking or vertical descending. Therefore, during vertical climbing, it seems likely that the galago supports its body mainly with the hindlimbs.