The cerebrum, cerebellum, and choroid plexuses from 16 patients with systemic amyloidosis, and the pituitary glands from 14 of these patients, were investigated histologically and immunohistochemically. Cerebrovascular amyloid (CVA) was found in the leptomeninges and cortices of six patients with systemic amyloidosis, including two patients with amyloid A protein (AA) amyloidosis related to serum amyloid A protein, one with AL amyloidosis related to immunoglobulin light chain (AL), two with familial type I amyloidotic polyneuropathy (FAP), and one with senile systemic amyloidosis (SSA). CVA protein from two patients with FAP reacted with anti-human prealbumin antibody similar to that of the visceral organs of these two patients. CVA in SSA reacted with anti-human prealbumin antibody and anti-beta protein antibody. Vascular amyloid was frequently noted in the pituitary glands and choroid plexuses of patients with systemic amyloidosis, and was found to be identical to that in the visceral organs (heart, kidney, and intestine) of these patients. CVA in the leptomeninges and cortices from two patients with AA amyloidosis and one with AL amyloidosis reacted with anti-beta protein monoclonal antibody but not with anti-human AA monoclonal antibody, anti-human A lambda antisera, and anti-human A kappa antisera. We suggest that amyloid proteins of AA and AL amyloidosis do not readily accumulate in the vessels in the leptomeninges and cortices even though the proteins circulate, and that beta protein is not derived from a serum precursor.