We assessed the faculty of confrontation naming and word fluency of the 11 patients afflicted with frontal lobe infarction or hemorrhage. All the patients were right-handed and manifested transcortical motor aphasia due to cerebrovascular diseases. We carried out the Western Aphasia Battery, and we adopted V-A; the naming task involved confrontation naming of 20 objects, and V-B; the word fluency task involved the naming as many animals as possible in a one minute period. Six patients who have lesions in the left medial frontal lobe performed excellency in the confrontation naming task but exhibited poor word fluency, and 5 patients who have lesions in the left dorso-lateral frontal lobe performed poorly in both tasks. This results suggests that the left dorso-lateral frontal lobe is important in confrontation naming, while the left medial frontal lobe is important in word fluency. Mushiake et al. (1991) showed that the premotor area was involved in visually guided sequential movements, and the supplementary motor area was involved internally determined sequential movements in primates. Regarding language function as analogous to movement, confrontation naming is analogous to visually guided movements and word fluency is analogous to internally determined movements. Thus, our results suggest that the functional difference between the left medial frontal lobe, which includes the supplementary motor area, and the left dorso-lateral frontal lobe, which includes the premotor area, which was demonstrated in primates for movement is also true of language function in humans.