This study used positron emission tomography (PET) to identify brain regions activated during the observation of grasping movements in normal, right-handed subjects. The experiment involved three conditions: observing grasping movements performed by an experimenter, performing the same grasping movements, and simply observing objects. Based on monkey data, it was hypothesized that the superior temporal sulcus (STS) and inferior area 6 would be activated during grasping observation. The findings in humans confirmed that grasping observation significantly activated the middle temporal gyrus, including the adjacent STS (Brodmann's area 21), and the caudal part of the left inferior frontal gyrus (Brodmann's area 45). The study also discussed the possible functional homologies between these areas and the monkey STS region and frontal area F5. The results suggest the presence of an observation-execution matching system in humans, with specific cortical areas selectively responsive to hand actions.This study used positron emission tomography (PET) to identify brain regions activated during the observation of grasping movements in normal, right-handed subjects. The experiment involved three conditions: observing grasping movements performed by an experimenter, performing the same grasping movements, and simply observing objects. Based on monkey data, it was hypothesized that the superior temporal sulcus (STS) and inferior area 6 would be activated during grasping observation. The findings in humans confirmed that grasping observation significantly activated the middle temporal gyrus, including the adjacent STS (Brodmann's area 21), and the caudal part of the left inferior frontal gyrus (Brodmann's area 45). The study also discussed the possible functional homologies between these areas and the monkey STS region and frontal area F5. The results suggest the presence of an observation-execution matching system in humans, with specific cortical areas selectively responsive to hand actions.