Uranyl acetate (UA) has been routinely used as a staining solution for ultrathin sections used in biological electron microscopy. As a radioactive nuclear material, UA is subject to strict international regulations. To develop an alternative and easy-to-use staining method for ultrathin sections, we examined various commercial light microscopic dyes. We found that Mayer's hematoxylin followed by Reynold's lead citrate solution showed staining results comparable to UA and Reynold's lead citrate solution, and this method is therefore suggested as a reliable and promising alternative to UA staining.