A differential staining method is described of myelinated fibres and nerve cell bodies applicable to sections of mammalian, including human, central nervous system specimens embedded in paraffin wax. Experimental and human necropsy material fixed in acetic paraformaldehyde in phosphate buffer was used. Sections of 15-20 microns in thickness were obtained, attached to slides, deparaffinized and hydrated. After hydration, sections are oxidized (30 s) in 2% potassium permanganate, bleached (1 min) in 5% oxalic acid and rinsed in distilled water. Staining is for 2-5 h in the following solution: 0.06% thionin, 1% formaldehyde, 10% acetic acid in distilled water. Sections are subsequently washed in distilled water, dehydrated through 96% and absolute ethanol, cleared in eucalyptol and mounted in Eukitt. Using the method described in the present paper, a differential coloration of myelin and neurons is obtained. Myelinated fibres appear red, whereas nerve cell bodies and glial nuclei are stained blue. This procedure provides a high contrast between myelin and cells suitable for observation and photography of sections. Simultaneous and differential coloration of both myelin and cells is easily and directly obtained with constant and homogeneous results.