Anterior cerebral artery territory infarction, which affects the medial frontal lobe and anterior part of the corpus callosum, may cause disinhibitory movement and behavioral disorders. The pathophysiology of disinhibitory movement and behavioral disorders was discussed in relation to the role of the frontal lobe in motor control and hemispheric asymmetry of motor functions. Instinctive grasp reaction is the prototype of disjunctive motor disinhibition syndromes, and diagnostic dyspraxia and compulsive manipulation of tools are the most illustrative forms. Diagnostic dyspraxia can be defined as uncontrolled cross-purposeful actions of the left hand triggered by voluntary activities of the left hand. In compulsive manipulation of tools, a patient, with the right hand, grasp and use tolls placed in front of them against the patient's will. The left hand often restrains the unintentional movement of the right hand in accordance with the patient's will. Utilization and imitation behaviors described by Lhermitte et al belong to disinhibitory behavioral disorders, in which volition of the patient or an individual as a whole is involved. External stimuli reflexively provoke the patient's will to act. The behaviors accordant with the will, even if inappropriate, are not compulsive, but the easily-raised volition in response to the stimuli is pathological. These disinhibitory disorders differ from disjunctive motor disinhibition syndromes because of lack of inconsistency between will and manifested behavior. Lesions in the frontal lobes has been suggested to be responsible for utilization and imitation behaviors.