Primary angiitis of the central nervous system (PACNS) is a form of vasculitis restricted to the brain and spinal cord, with protean clinical manifestations and often slowly progressive course. Outcomes vary, ranging from spontaneous resolution to rapid decline and death. Diagnosis of PACNS is based on angiography and/or biopsy. We reviewed surgical biopsies from 46 patients (53 biopsies) with PACNS, including 25 men and 21 women (median age 46, range: 25 to 84 y) and correlated the findings with relevant clinical parameters. Biopsies (51 brain, 2 spinal) were diagnostic of vasculitis in 29 (63%) patients. Three morphologic patterns of vasculitis were observed: acute necrotizing (n=4, 14%); purely lymphocytic (n=8, 28%); and granulomatous (n=17, 58%), 8 associated with deposition of beta-A4 amyloid. Biopsies not diagnostic of PACNS (n=17, 37%) showed nonspecific gliosis (53%), mild perivascular mononuclear inflammation (18%), and parenchymal ischemic damage/infarct (18%). All positive biopsies were among those directed to an imaging abnormality (targeted biopsies) and biopsies including leptomeninges were more often positive than those that did not. Thus, where possible, a targeted biopsy that includes leptomeninges is recommended to maximize diagnostic potential. No statistically significant differences in outcome were noted among the 3 histopathologic groups or when comparing biopsy positive versus biopsy negative PACNS groups. Overall the outcomes were relatively favorable, with only 14% mortality or severe morbidity at 1.14 years (mean) after biopsy.