We report a 67-year-old left-handed man who exhibited an ideational apraxia in both clinical and nonclinical natural settings following a right hemisphere infarction. His inability to use tools could not be explained by a motor production deficit (ideomotor apraxia), because he made content errors and could not match tools with objects. His deficit could not be attributed to an agnosia or language comprehension deficit, because he could name tools and point to tools on command. Based on our testing, it appeared that this patient had a loss of knowledge related to tool use.