Cell types associated with angiotensinogen mRNA in rat brain were identified in individual brain sections by in situ hybridization with tritiated RNA probes or with a sulfur-35—labeled oligonucleotide combined with immunocytochemical detection of either glial fibrillary acidic protein (GFAP) for astrocytes or microtubule-associated protein (MAP-2) for neurons. Autoradiography revealed silver grains clustered primarily over GFAP-reactive soma and processes; most grain clusters were not associated with MAP-2—reactive cells. These results demonstrate that, in contrast to other known neuropeptide precursors, angiotensinogen is synthesized by glia.