Action observation is a useful approach for improving human motor skill acquisition. This process involves the mirror neuron system that consists of the ventral premotor area, inferior parietal lobule, and superior temporal sulcus. The interaction between these areas produces the effect of action observation. This chapter presents neurophysiological and brain imaging studies of action observation, and their application to human motor learning. For action observation, the mirror system appears to map the intention in the ventral premotor area and the goal in the inferior parietal lobule. These features of action representation may be useful for refining conditions of practice, based on the mirror system, for acquiring new motor skills.