Purpose: To evaluate changes in lower extremity muscle activity caused by high heeled shoe wearing during normal, brisk, and upslope walking. Methods: Twenty healthy young women (age, $23.9{pm}2.47$) participated in this study. Muscle activities of the tibialis anterior, peroneus longus, gastrocnemius lateralis, gastrocnemius medialis, soleus, hamstring, vastus lateralis, and vastus medialis while walking normally, walking briskly, and walking up a slope. Results: When walking normally, the peroneus longus, gastrocnemius lateralis, soleus, and vastus lateralis evidenced higher activity when high-heeled shoes were worn (p<0.05). During brisk walking, the peroneus longus and gastrocnemius lateralis exhibited higher activity (p<0.05). Although the peroneus longus and vastus lateralis exhibited higher activity when walking up an incline with high-heeled shoes, the activity levels of the tibialis anterior and gastrocnemius medialis were lower (p<0.05). Conclusion: The results of this study demonstrate that increased heel height substantially reduces muscle effort when walking up a slope. From a therapeutic perspective, it is possible that using high heeled shoes over a short period might enhance muscle activity of ankle evertor, although it can cause mediolateral muscle imbalances in the lower extremities.