BACKGROUND: The frontal-subcortical circuits link the specific areas of the frontal cortex to the striatum, basal ganglia, and thalamus. Disruption of the frontal-subcortical circuits may lead to cognitive impairment with frontal lobe features. The putamen is a central component of frontal-subcortical circuits. Although putaminal lesions presumably lead to cognitive and behavioral changes, studies on frontal lobe dysfunctions after putaminal stroke are scarce. There are no previous studies that systematically examined frontal lobe functions with a focal putaminal lesion. The objective of this study is to demonstrate whether putaminal hemorrhage causes frontal lobe dysfunction. METHODS: Cognitive functions, including various aspects of frontal lobe functions, were systematically assessed in 15 patients with left- or right-sided putaminal hemorrhage 2 months after the onset and compared with healthy controls. RESULTS: Patients did not have signs of aphasia, apraxia, or spatial neglect. They performed significantly worse on tests of frontal lobe function, including Letter-Number Sequencing (U = 22, P < .001), lexical fluency (U = 30, P < .001), and motor series subtest (U = 45, P = .004) of the Frontal Assessment Battery. On the Wisconsin Card Sorting Test, patients performed significantly worse for "categories achieved" (U = 29.5, P < .001), "perseverative errors" (U = 25, P < .001), and "set loss" (U = 49, P = .008). None showed behavioral impairment. CONCLUSIONS: Isolated putaminal hemorrhage causes modest frontal lobe dysfunction without behavioral symptoms. Our findings indicate that isolated putaminal hemorrhage disrupts the dorsolateral-striato-pallido-thalamic circuits and causes executive dysfunction.