Two cases of histologically documented primary cerebral amyloid complicated by spontaneous intracerebral hematoma are reported. The neurosurgical implications of this disease are reviewed briefly. Immunological studies in one patient, believed to be a rare survivor of an intracerebral hemorrhage from nonfamilial primary cerebral amyloid angiopathy, demonstrated an increased percentage of B cells within both the cerebrospinal fluid (CSF) and the blood compartments. Hypofunction of CSF concanavalin A-activated suppressor cells with respect to B and T cell targets was shown. The blood suppressor cells from the patient were similar to those of an age-matched control. Compartmental central nervous system suppressor cell dysfunction resulting in B cell activation could play a role in facilitating amyloid deposits in the brain. The mechanisms responsible for the compartmental and limited suppressor cell dysfunction are unknown.