Weber's syndrome is one of the classically described brainstem syndromes. The mesencephalic artery and the syndromes resulting from occlusion of its branches have been attracting increasing interest in the past few years. We present here a case of Weber's syndrome emphasizing that (1) it is one of the major syndromes deriving from infarction in the territory of the mesencephalic artery; (2) that at least two clinical patterns of Weber's syndrome may be distinguished on the basis of the presence or lack of abnormal somnolence, mental confusion, and abulia; and (3) that each one of these patterns seems to be correlated with damage to distinct zones within the general territory of the mesencephalic artery.