A simple cytological method for the selective impregnation of neuronal "nuclear bodies" is described. This procedure involves glutaraldehyde fixation, pretreatment with methanol-acetic acid, impregnation in a 1.5% colloidal solution of silver nitrate containing gelatin, and pyrogallic reduction of whole tissue blocks. After block staining the material was either dehydrated and embedded in araldite for light and electron microscopy studies, or processed for the elaboration of neuronal smear preparations, which were used for the quantitative analysis of nuclear bodies. By light microscopy, nuclear bodies appear as conspicuous, intensely impregnated inclusions, 0.3-0.9 micron in diameter. Both the nucleoli and cytoplasmic Nissl bodies can be counterstained with Toluidine blue. Overimpregnation produces an additional staining of the nucleolar fibrillar component.