To identify the functional fields involved in grasping for objects, we measured regional cerebral blood flow (rCBF) by positron emission tomography (PET) in eight normal volunteers. In the reaching and grasping tasks, the subjects were asked to touch or grasp one of five cylinders with their finger(s). Compared with reaching, grasping specifically increased the rCBF in the fields located in the bilateral premotor area (PMA), the posterior parietal area (PPA) and the prefrontal area (PFA). These results indicate that PMA, PPA and PFA might be key structures for the performance of grasping movements.