A series of 15 arteriovenous malformations (AVMs) of the corpus callosum--9% of 170 intracranial AVMs admitted to the School of Medicine of the University of Rome during a 30-yr period--was studied. In all cases the lesion concerned mainly the corpus callosum, although in some it also involved the surrounding structures, such as septum pellucidum, tela choroidea, and the mesial hemisphere. These malformations are divided into three groups, namely, those involving mainly the genu, the truncus, or the splenium of the corpus callosum. The last predominated in the present series. Each type has a peculiar angiographic appearance. In general these lesions are fed by branches from the anterior cerebral and/or posterior cerebral arteries, although in some cases minor contributions from the middle cerebral artery may also be present. Vascularization is often bilateral. Venous drainage occurs through the inferior and/or superior sagittal sinuses and/or the Galen system. As to clinical presentation, Subarachnoid Hemorrhage (SAH) is the usual presenting symptom and tends to recur frequently. Neurological localizing symptoms are infrequent, as are seizures; psychological symptoms are an exception. Of the 4 cases managed conservatively, only one had no further episodes of bleeding and remained free of complaints. On the other hand, surgical results of the 11 operated patients were satisfactory, in the sense that no mortality and low morbidity were recorded. Accordingly, surgical treatment of AVMs of the corpus callosum is recommended as a rule