AbstractToluidine blue stain has been widely used for staining undecalcified bone sections, but previous techniques required removal of embedding plastic or surface etching with both alcohol and acid solutions. In this study, solutions of toluidine blue at different pHs were used to stain unetched and acidetched sections. A group of the test staining solutions were heated in an effort to enhance section staining. Acid-etching prior to staining was found to be necessary to achieve bone matrix staining, but methanol etching could be eliminated if staining solutions were heated to 55–60°C. Sections stained with the heated solutions buffered to pH 7.0 or 8.0 had optimum morphology. (The J Histotechnol17:357, 1994)