A method is described for the histochemical detection of horseradish peroxidase in Paraplast Plus® embedded brain sections. The procedure uses 150-µm-thick Vibratome-cut slices of glutaraldehyde-paraformaldehyde-fixed brain tissue. Tetramethylbenzidine stabilized by diaminobenzidine/cobalt/H202 is used as chromogen. The Vibratome-cut slices are dehydrated through a graded series of acetone, cleared in toluol and flat-embedded in Paraplast Plus embedding medium. Serial sections can be cut as thin as 5–7 µm.The method is universal in its application and permits optimal visualization of labeled neurons with great morphological detail at the light-microscopic l