Eleven cases of cerebral cavernous angiomas (cavernomas) were observed within a period of 3 years. Two patients presented with cerebral hemorrhage, five with epilepsy, three each with a progressive focal neurological deficit, and one with papilledema. The unruptured lesions had a heterogeneous density on computed tomography with relatively little contrast enhancement. Two lesions contained major cysts. In one of these cases, the cyst measured 5.5 cm in diameter, had an enhancing membrane, and was surrounded by brain edema. Angiography did not show hypervascularity in any instance. During exploration and histological processing, special attention was paid to signs of previous silent hemorrhages and to the degree of encapsulation of the lesion. Iron deposits (signs of previous hemorrhages) were seen to varying degrees inside all cavernomas as well as in the surrounding gliotic cerebrum, and a causal relation between iron deposits and epileptic seizures seems likely. Encapsulation was minimal with the ruptured cavernomas and particularly prominent with the cystic lesions. The membrane of the giant cystic lesion with peripheral brain edema had a histological structure similar to that of the membranes of chronic subdural hematomas. It is suggested that continuous growth of cavernoma cysts is the result of recurrent hemorrhages from sinusoids of the malformation and from the neocapillary network of the cyst membranes.