In this study we compared the recently commercialized electron microscopy embedding resin Unicryl with the well-known resin Lowicryl K4M with regard to morphological and immunohistochemical preservation properties. The standard embedding procedure recommended by the manufacturer for the use of Unicryl resulted in considerable morphological alterations of the tissue, with the appearance of large gaps in and between the cells of the examined tissue. Morphometric analysis pointed to a swelling of the extracellular matrix as the main cause of these morphological artifacts. A slight modification in the protocol to correct this artifact is proposed and tested. Immunohistochemically, tissue embedded in Unicryl resulted in a significantly stronger immunogold labeling than identical tissue embedded in Lowicryl K4M. From the results of this technical study, it can be concluded that Unicryl embedding is a valuable new tool to supplement the available techniques for immunoelectron microscopic studies.