The lenticulostriate arteries are the subject of a microanatomical study on 50 formalin fixed human brains. A single trunk arising from the middle cerebral artery is rarely found. In fact the branches are numerous and they are found to ramify before penetrating the anterior perforated substance. The length of the sphenoidal segment is variable and this aspect is discussed in the light of the literature data. The origin of the perforating branches is spread from the internal carotid artery to the bifurcation branches of the middle cerebral artery (M2 segment). On the other hand lenticulostriate arteries arising from the cortical branches of the middle cerebral artery are often found. These anatomical patterns are of essentially surgical interest. No branches must be damaged during the opening of the Sylvian fissure or during the dissection of an aneurysm in this region.